# Note: This documents additional properties of any device beyond what
-# is documented in Documentation/sysfs-rules.txt
+# is documented in Documentation/admin-guide/sysfs-rules.rst
What: /sys/devices/*/of_node
Date: February 2015
in the initramfs, which has already been measured as part
of the trusted boot. For more information on creating and
loading existing trusted/encrypted keys, refer to:
- Documentation/keys-trusted-encrypted.txt. (A sample dracut
- patch, which loads the trusted/encrypted key and enables
+ Documentation/security/keys/trusted-encrypted.rst. (A sample
+ dracut patch, which loads the trusted/encrypted key and enables
EVM, is available from http://linux-ima.sourceforge.net/#EVM.)
This switch controls the boost setting for the whole system.
Boosting allows the CPU and the firmware to run at a frequency
beyound it's nominal limit.
- More details can be found in Documentation/cpu-freq/boost.txt
+ More details can be found in
+ Documentation/admin-guide/pm/cpufreq.rst
What: /sys/devices/system/cpu/cpu#/crash_notes
no_turbo: limits the driver to selecting P states below the turbo
frequency range.
- More details can be found in Documentation/cpu-freq/intel-pstate.txt
+ More details can be found in
+ Documentation/admin-guide/pm/intel_pstate.rst
What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
Date: July 2014(documented, existed before August 2008)
Writing one of the above strings to this file causes the system
to transition into the corresponding state, if available.
- See Documentation/power/states.txt for more information.
+ See Documentation/admin-guide/pm/sleep-states.rst for more
+ information.
What: /sys/power/mem_sleep
Date: November 2016
represented by it to be used on subsequent attempts to suspend
the system.
- See Documentation/power/states.txt for more information.
+ See Documentation/admin-guide/pm/sleep-states.rst for more
+ information.
What: /sys/power/disk
Date: September 2006
# The following targets are independent of HAVE_SPHINX, and the rules should
# work or silently pass without Sphinx.
+refcheckdocs:
+ $(Q)cd $(srctree);scripts/documentation-file-ref-check
+
cleandocs:
$(Q)rm -rf $(BUILDDIR)
$(Q)$(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media clean
@echo ' epubdocs - EPUB'
@echo ' xmldocs - XML'
@echo ' linkcheckdocs - check for broken external links (will connect to external hosts)'
+ @echo ' refcheckdocs - check for references to non-existing files under Documentation'
@echo ' cleandocs - clean all generated files'
@echo
@echo ' make SPHINXDIRS="s1 s2" [target] Generate only docs of folder s1, s2'
@echo
@echo ' make SPHINX_CONF={conf-file} [target] use *additional* sphinx-build'
@echo ' configuration. This is e.g. useful to build with nit-picking config.'
+ @echo
+ @echo ' Default location for the generated documents is Documentation/output'
This straightforward approach had the disadvantage of needing to
account for POSIX signals sent to user tasks,
so more recent implemementations use the Linux kernel's
-<a href="https://www.kernel.org/doc/Documentation/workqueue.txt">workqueues</a>.
+<a href="https://www.kernel.org/doc/Documentation/core-api/workqueue.rst">workqueues</a>.
<p>
The requesting task still does counter snapshotting and funnel-lock
help debugging the problem. The text above the dump is also
important: it tells something about why the kernel dumped code (in
the above example, it's due to a bad kernel pointer). More information
- on making sense of the dump is in Documentation/admin-guide/oops-tracing.rst
+ on making sense of the dump is in Documentation/admin-guide/bug-hunting.rst
- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
as is, otherwise you will have to use the ``ksymoops`` program to make
used for the development of the affected code. This can be done by using
the ``get_maintainer.pl`` script.
-For example, if you find a bug at the gspca's conex.c file, you can get
+For example, if you find a bug at the gspca's sonixj.c file, you can get
their maintainers with::
$ ./scripts/get_maintainer.pl -f drivers/media/usb/gspca/sonixj.c
Tejun and Bhaktipriya (in this specific case, none really envolved on the
development of this file);
- The driver maintainer (Hans Verkuil);
-- The subsystem maintainer (Mauro Carvalho Chehab)
+- The subsystem maintainer (Mauro Carvalho Chehab);
- The driver and/or subsystem mailing list (linux-media@vger.kernel.org);
- the Linux Kernel mailing list (linux-kernel@vger.kernel.org).
--------------
If you know programming, you could help us by not only reporting the bug,
-but also providing us with a solution. After all open source is about
+but also providing us with a solution. After all, open source is about
sharing what you do and don't you want to be recognised for your genius?
If you decide to take this way, once you have worked out a fix please submit
it upstream.
Please do read
-ref:`Documentation/process/submitting-patches.rst <submittingpatches>` though
+:ref:`Documentation/process/submitting-patches.rst <submittingpatches>` though
to help your code get accepted.
amijoy.map= [HW,JOY] Amiga joystick support
Map of devices attached to JOY0DAT and JOY1DAT
Format: <a>,<b>
- See also Documentation/input/joystick.txt
+ See also Documentation/input/joydev/joystick.rst
analog.map= [HW,JOY] Analog joystick and gamepad support
Specifies type or capabilities of an analog joystick
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
bttv.radio= Most important insmod options are available as
kernel args too.
- bttv.pll= See Documentation/video4linux/bttv/Insmod-options
+ bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
bttv.tuner=
bulk_remove=off [PPC] This parameter disables the use of the pSeries
For now, only VisioBraille is supported.
consoleblank= [KNL] The console blank (screen saver) timeout in
- seconds. Defaults to 10*60 = 10mins. A value of 0
- disables the blank timer.
+ seconds. A value of 0 disables the blank timer.
+ Defaults to 0.
coredump_filter=
[KNL] Change the default value for
db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
(one device per port)
Format: <port#>,<type>
- See also Documentation/input/joystick-parport.txt
+ See also Documentation/input/devices/joystick-parport.rst
ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
time. See
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
support via parallel port (up to 5 devices per port)
Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
- See also Documentation/input/joystick-parport.txt
+ See also Documentation/input/devices/joystick-parport.rst
gamma= [HW,DRM]
ivrs_acpihid[00:14.5]=AMD0020:0
js= [HW,JOY] Analog joystick
- See Documentation/input/joystick.txt.
+ See Documentation/input/joydev/joystick.rst.
nokaslr [KNL]
When CONFIG_RANDOMIZE_BASE is set, this disables
s2idle - Suspend-To-Idle
shallow - Power-On Suspend or equivalent (if supported)
deep - Suspend-To-RAM or equivalent (if supported)
- See Documentation/power/states.txt.
+ See Documentation/admin-guide/pm/sleep-states.rst.
meye.*= [HW] Set MotionEye Camera parameters
- See Documentation/video4linux/meye.txt.
+ See Documentation/media/v4l-drivers/meye.rst.
mfgpt_irq= [IA-32] Specify the IRQ to use for the
Multi-Function General Purpose Timers on AMD Geode
plip= [PPT,NET] Parallel port network link
Format: { parport<nr> | timid | 0 }
- See also Documentation/parport.txt.
+ See also Documentation/admin-guide/parport.rst.
pmtmr= [X86] Manual setup of pmtmr I/O Port.
Override pmtimer IOPort with a hex value.
[KNL] Should the soft-lockup detector generate panics.
Format: <integer>
+ A nonzero value instructs the soft-lockup detector
+ to panic the machine when a soft-lockup occurs. This
+ is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
+ which is the respective build-time switch to that
+ functionality.
+
softlockup_all_cpu_backtrace=
[KNL] Should the soft-lockup detector generate
backtraces on all cpus.
TurboGraFX parallel port interface
Format:
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
- See also Documentation/input/joystick-parport.txt
+ See also Documentation/input/devices/joystick-parport.rst
udbg-immortal [PPC] When debugging early kernel crashes that
happen after console_init() and before a proper
If the failure includes an "OOPS:", take a picture of the screen, capture
a netconsole trace, or type the message from your screen into the bug
-report. Please read "Documentation/admin-guide/oops-tracing.rst" before posting your
+report. Please read "Documentation/admin-guide/bug-hunting.rst" before posting your
bug report. This explains what you should do with the "Oops" information
to make it useful to the recipient.
[4.2.] Kernel .config file:
[5.] Most recent kernel version which did not have the bug:
[6.] Output of Oops.. message (if applicable) with symbolic information
- resolved (see Documentation/admin-guide/oops-tracing.rst)
+ resolved (see Documentation/admin-guide/bug-hunting.rst)
[7.] A small shell script or example program which triggers the
problem (if possible)
[8.] Environment
(to compile support as a module which can be loaded and unloaded)
to the options:
- Enhanced IDE/MFM/RLL disk/cdrom/tape/floppy support
+ ATA/ATAPI/MFM/RLL support
Include IDE/ATAPI CDROM support
- and `no' to
-
- Use old disk-only driver on primary interface
-
Depending on what type of IDE interface you have, you may need to
specify additional configuration options. See
Documentation/ide/ide.txt.
The Linux Kernel API
====================
-Data Types
-==========
-Doubly Linked Lists
--------------------
+List Management Functions
+=========================
.. kernel-doc:: include/linux/list.h
:internal:
Bitmap Operations
-----------------
+.. kernel-doc:: lib/bitmap.c
+ :doc: bitmap introduction
+
+.. kernel-doc:: include/linux/bitmap.h
+ :doc: declare bitmap
+
+.. kernel-doc:: include/linux/bitmap.h
+ :doc: bitmap overview
+
+.. kernel-doc:: include/linux/bitmap.h
+ :doc: bitmap bitops
+
.. kernel-doc:: lib/bitmap.c
:export:
.. kernel-doc:: lib/bitmap.c
:internal:
+.. kernel-doc:: include/linux/bitmap.h
+ :internal:
+
Command-line Parsing
--------------------
CRC Functions
-------------
+.. kernel-doc:: lib/crc4.c
+ :export:
+
.. kernel-doc:: lib/crc7.c
:export:
-.. kernel-doc:: lib/crc16.c
+.. kernel-doc:: lib/crc8.c
:export:
-.. kernel-doc:: lib/crc-itu-t.c
+.. kernel-doc:: lib/crc16.c
:export:
.. kernel-doc:: lib/crc32.c
.. kernel-doc:: lib/crc-ccitt.c
:export:
+.. kernel-doc:: lib/crc-itu-t.c
+ :export:
+
idr/ida Functions
-----------------
.. kernel-doc:: lib/idr.c
:export:
+Math Functions in Linux
+=======================
+
+Base 2 log and power Functions
+------------------------------
+
+.. kernel-doc:: include/linux/log2.h
+ :internal:
+
+Division Functions
+------------------
+
+.. kernel-doc:: include/asm-generic/div64.h
+ :functions: do_div
+
+.. kernel-doc:: include/linux/math64.h
+ :internal:
+
+.. kernel-doc:: lib/div64.c
+ :functions: div_s64_rem div64_u64_rem div64_u64 div64_s64
+
+.. kernel-doc:: lib/gcd.c
+ :export:
+
Memory Management in Linux
==========================
provide some progress information as Coccinelle moves forward with
work.
-DEBUG_FILE support is only supported when using coccinelle >= 1.2.
+DEBUG_FILE support is only supported when using coccinelle >= 1.0.2.
.cocciconfig support
--------------------
Note that some tests will require root privileges.
+Build and run from user specific object directory (make O=dir)::
+
+ $ make O=/tmp/kselftest kselftest
+
+Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=)::
+
+ $ make KBUILD_OUTPUT=/tmp/kselftest kselftest
+
+The above commands run the tests and print pass/fail summary to make it
+easier to understand the test results. Please find the detailed individual
+test results for each test in /tmp/testname file(s).
Running a subset of selftests
=============================
$ make TARGETS="size timers" kselftest
+Build and run from user specific object directory (make O=dir)::
+
+ $ make O=/tmp/kselftest TARGETS="size timers" kselftest
+
+Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=)::
+
+ $ make KBUILD_OUTPUT=/tmp/kselftest TARGETS="size timers" kselftest
+
+The above commands run the tests and print pass/fail summary to make it
+easier to understand the test results. Please find the detailed individual
+test results for each test in /tmp/testname file(s).
+
See the top-level tools/testing/selftests/Makefile for the list of all
possible targets.
-
Running the full range hotplug selftests
========================================
* Use TEST_GEN_XXX if such binaries or files are generated during
compiling.
- TEST_PROGS, TEST_GEN_PROGS mean it is the excutable tested by
+ TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by
default.
+ TEST_CUSTOM_PROGS should be used by tests that require custom build
+ rule and prevent common build rule use.
+
+ TEST_PROGS are for test shell scripts. Please ensure shell script has
+ its exec bit set. Otherwise, lib.mk run_tests will generate a warning.
+
+ TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.
+
TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
executable which is not tested by default.
TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
+++ /dev/null
-00-INDEX
- - this file.
-client.txt
- -the DMA Engine API Guide.
-dmatest.txt
- - how to compile, configure and use the dmatest system.
-provider.txt
- - the DMA controller API.
\ No newline at end of file
+++ /dev/null
- DMA Engine API Guide
- ====================
-
- Vinod Koul <vinod dot koul at intel.com>
-
-NOTE: For DMA Engine usage in async_tx please see:
- Documentation/crypto/async-tx-api.txt
-
-
-Below is a guide to device driver writers on how to use the Slave-DMA API of the
-DMA Engine. This is applicable only for slave DMA usage only.
-
-The slave DMA usage consists of following steps:
-1. Allocate a DMA slave channel
-2. Set slave and controller specific parameters
-3. Get a descriptor for transaction
-4. Submit the transaction
-5. Issue pending requests and wait for callback notification
-
-1. Allocate a DMA slave channel
-
- Channel allocation is slightly different in the slave DMA context,
- client drivers typically need a channel from a particular DMA
- controller only and even in some cases a specific channel is desired.
- To request a channel dma_request_chan() API is used.
-
- Interface:
- struct dma_chan *dma_request_chan(struct device *dev, const char *name);
-
- Which will find and return the 'name' DMA channel associated with the 'dev'
- device. The association is done via DT, ACPI or board file based
- dma_slave_map matching table.
-
- A channel allocated via this interface is exclusive to the caller,
- until dma_release_channel() is called.
-
-2. Set slave and controller specific parameters
-
- Next step is always to pass some specific information to the DMA
- driver. Most of the generic information which a slave DMA can use
- is in struct dma_slave_config. This allows the clients to specify
- DMA direction, DMA addresses, bus widths, DMA burst lengths etc
- for the peripheral.
-
- If some DMA controllers have more parameters to be sent then they
- should try to embed struct dma_slave_config in their controller
- specific structure. That gives flexibility to client to pass more
- parameters, if required.
-
- Interface:
- int dmaengine_slave_config(struct dma_chan *chan,
- struct dma_slave_config *config)
-
- Please see the dma_slave_config structure definition in dmaengine.h
- for a detailed explanation of the struct members. Please note
- that the 'direction' member will be going away as it duplicates the
- direction given in the prepare call.
-
-3. Get a descriptor for transaction
-
- For slave usage the various modes of slave transfers supported by the
- DMA-engine are:
-
- slave_sg - DMA a list of scatter gather buffers from/to a peripheral
- dma_cyclic - Perform a cyclic DMA operation from/to a peripheral till the
- operation is explicitly stopped.
- interleaved_dma - This is common to Slave as well as M2M clients. For slave
- address of devices' fifo could be already known to the driver.
- Various types of operations could be expressed by setting
- appropriate values to the 'dma_interleaved_template' members.
-
- A non-NULL return of this transfer API represents a "descriptor" for
- the given transaction.
-
- Interface:
- struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
- struct dma_chan *chan, struct scatterlist *sgl,
- unsigned int sg_len, enum dma_data_direction direction,
- unsigned long flags);
-
- struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
- struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
- size_t period_len, enum dma_data_direction direction);
-
- struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
- struct dma_chan *chan, struct dma_interleaved_template *xt,
- unsigned long flags);
-
- The peripheral driver is expected to have mapped the scatterlist for
- the DMA operation prior to calling dmaengine_prep_slave_sg(), and must
- keep the scatterlist mapped until the DMA operation has completed.
- The scatterlist must be mapped using the DMA struct device.
- If a mapping needs to be synchronized later, dma_sync_*_for_*() must be
- called using the DMA struct device, too.
- So, normal setup should look like this:
-
- nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
- if (nr_sg == 0)
- /* error */
-
- desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
-
- Once a descriptor has been obtained, the callback information can be
- added and the descriptor must then be submitted. Some DMA engine
- drivers may hold a spinlock between a successful preparation and
- submission so it is important that these two operations are closely
- paired.
-
- Note:
- Although the async_tx API specifies that completion callback
- routines cannot submit any new operations, this is not the
- case for slave/cyclic DMA.
-
- For slave DMA, the subsequent transaction may not be available
- for submission prior to callback function being invoked, so
- slave DMA callbacks are permitted to prepare and submit a new
- transaction.
-
- For cyclic DMA, a callback function may wish to terminate the
- DMA via dmaengine_terminate_async().
-
- Therefore, it is important that DMA engine drivers drop any
- locks before calling the callback function which may cause a
- deadlock.
-
- Note that callbacks will always be invoked from the DMA
- engines tasklet, never from interrupt context.
-
-4. Submit the transaction
-
- Once the descriptor has been prepared and the callback information
- added, it must be placed on the DMA engine drivers pending queue.
-
- Interface:
- dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
-
- This returns a cookie can be used to check the progress of DMA engine
- activity via other DMA engine calls not covered in this document.
-
- dmaengine_submit() will not start the DMA operation, it merely adds
- it to the pending queue. For this, see step 5, dma_async_issue_pending.
-
-5. Issue pending DMA requests and wait for callback notification
-
- The transactions in the pending queue can be activated by calling the
- issue_pending API. If channel is idle then the first transaction in
- queue is started and subsequent ones queued up.
-
- On completion of each DMA operation, the next in queue is started and
- a tasklet triggered. The tasklet will then call the client driver
- completion callback routine for notification, if set.
-
- Interface:
- void dma_async_issue_pending(struct dma_chan *chan);
-
-Further APIs:
-
-1. int dmaengine_terminate_sync(struct dma_chan *chan)
- int dmaengine_terminate_async(struct dma_chan *chan)
- int dmaengine_terminate_all(struct dma_chan *chan) /* DEPRECATED */
-
- This causes all activity for the DMA channel to be stopped, and may
- discard data in the DMA FIFO which hasn't been fully transferred.
- No callback functions will be called for any incomplete transfers.
-
- Two variants of this function are available.
-
- dmaengine_terminate_async() might not wait until the DMA has been fully
- stopped or until any running complete callbacks have finished. But it is
- possible to call dmaengine_terminate_async() from atomic context or from
- within a complete callback. dmaengine_synchronize() must be called before it
- is safe to free the memory accessed by the DMA transfer or free resources
- accessed from within the complete callback.
-
- dmaengine_terminate_sync() will wait for the transfer and any running
- complete callbacks to finish before it returns. But the function must not be
- called from atomic context or from within a complete callback.
-
- dmaengine_terminate_all() is deprecated and should not be used in new code.
-
-2. int dmaengine_pause(struct dma_chan *chan)
-
- This pauses activity on the DMA channel without data loss.
-
-3. int dmaengine_resume(struct dma_chan *chan)
-
- Resume a previously paused DMA channel. It is invalid to resume a
- channel which is not currently paused.
-
-4. enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
- dma_cookie_t cookie, dma_cookie_t *last, dma_cookie_t *used)
-
- This can be used to check the status of the channel. Please see
- the documentation in include/linux/dmaengine.h for a more complete
- description of this API.
-
- This can be used in conjunction with dma_async_is_complete() and
- the cookie returned from dmaengine_submit() to check for
- completion of a specific DMA transaction.
-
- Note:
- Not all DMA engine drivers can return reliable information for
- a running DMA channel. It is recommended that DMA engine users
- pause or stop (via dmaengine_terminate_all()) the channel before
- using this API.
-
-5. void dmaengine_synchronize(struct dma_chan *chan)
-
- Synchronize the termination of the DMA channel to the current context.
-
- This function should be used after dmaengine_terminate_async() to synchronize
- the termination of the DMA channel to the current context. The function will
- wait for the transfer and any running complete callbacks to finish before it
- returns.
-
- If dmaengine_terminate_async() is used to stop the DMA channel this function
- must be called before it is safe to free memory accessed by previously
- submitted descriptors or to free any resources accessed within the complete
- callback of previously submitted descriptors.
-
- The behavior of this function is undefined if dma_async_issue_pending() has
- been called between dmaengine_terminate_async() and this function.
+++ /dev/null
-DMAengine controller documentation
-==================================
-
-Hardware Introduction
-+++++++++++++++++++++
-
-Most of the Slave DMA controllers have the same general principles of
-operations.
-
-They have a given number of channels to use for the DMA transfers, and
-a given number of requests lines.
-
-Requests and channels are pretty much orthogonal. Channels can be used
-to serve several to any requests. To simplify, channels are the
-entities that will be doing the copy, and requests what endpoints are
-involved.
-
-The request lines actually correspond to physical lines going from the
-DMA-eligible devices to the controller itself. Whenever the device
-will want to start a transfer, it will assert a DMA request (DRQ) by
-asserting that request line.
-
-A very simple DMA controller would only take into account a single
-parameter: the transfer size. At each clock cycle, it would transfer a
-byte of data from one buffer to another, until the transfer size has
-been reached.
-
-That wouldn't work well in the real world, since slave devices might
-require a specific number of bits to be transferred in a single
-cycle. For example, we may want to transfer as much data as the
-physical bus allows to maximize performances when doing a simple
-memory copy operation, but our audio device could have a narrower FIFO
-that requires data to be written exactly 16 or 24 bits at a time. This
-is why most if not all of the DMA controllers can adjust this, using a
-parameter called the transfer width.
-
-Moreover, some DMA controllers, whenever the RAM is used as a source
-or destination, can group the reads or writes in memory into a buffer,
-so instead of having a lot of small memory accesses, which is not
-really efficient, you'll get several bigger transfers. This is done
-using a parameter called the burst size, that defines how many single
-reads/writes it's allowed to do without the controller splitting the
-transfer into smaller sub-transfers.
-
-Our theoretical DMA controller would then only be able to do transfers
-that involve a single contiguous block of data. However, some of the
-transfers we usually have are not, and want to copy data from
-non-contiguous buffers to a contiguous buffer, which is called
-scatter-gather.
-
-DMAEngine, at least for mem2dev transfers, require support for
-scatter-gather. So we're left with two cases here: either we have a
-quite simple DMA controller that doesn't support it, and we'll have to
-implement it in software, or we have a more advanced DMA controller,
-that implements in hardware scatter-gather.
-
-The latter are usually programmed using a collection of chunks to
-transfer, and whenever the transfer is started, the controller will go
-over that collection, doing whatever we programmed there.
-
-This collection is usually either a table or a linked list. You will
-then push either the address of the table and its number of elements,
-or the first item of the list to one channel of the DMA controller,
-and whenever a DRQ will be asserted, it will go through the collection
-to know where to fetch the data from.
-
-Either way, the format of this collection is completely dependent on
-your hardware. Each DMA controller will require a different structure,
-but all of them will require, for every chunk, at least the source and
-destination addresses, whether it should increment these addresses or
-not and the three parameters we saw earlier: the burst size, the
-transfer width and the transfer size.
-
-The one last thing is that usually, slave devices won't issue DRQ by
-default, and you have to enable this in your slave device driver first
-whenever you're willing to use DMA.
-
-These were just the general memory-to-memory (also called mem2mem) or
-memory-to-device (mem2dev) kind of transfers. Most devices often
-support other kind of transfers or memory operations that dmaengine
-support and will be detailed later in this document.
-
-DMA Support in Linux
-++++++++++++++++++++
-
-Historically, DMA controller drivers have been implemented using the
-async TX API, to offload operations such as memory copy, XOR,
-cryptography, etc., basically any memory to memory operation.
-
-Over time, the need for memory to device transfers arose, and
-dmaengine was extended. Nowadays, the async TX API is written as a
-layer on top of dmaengine, and acts as a client. Still, dmaengine
-accommodates that API in some cases, and made some design choices to
-ensure that it stayed compatible.
-
-For more information on the Async TX API, please look the relevant
-documentation file in Documentation/crypto/async-tx-api.txt.
-
-DMAEngine Registration
-++++++++++++++++++++++
-
-struct dma_device Initialization
---------------------------------
-
-Just like any other kernel framework, the whole DMAEngine registration
-relies on the driver filling a structure and registering against the
-framework. In our case, that structure is dma_device.
-
-The first thing you need to do in your driver is to allocate this
-structure. Any of the usual memory allocators will do, but you'll also
-need to initialize a few fields in there:
-
- * channels: should be initialized as a list using the
- INIT_LIST_HEAD macro for example
-
- * src_addr_widths:
- - should contain a bitmask of the supported source transfer width
-
- * dst_addr_widths:
- - should contain a bitmask of the supported destination transfer
- width
-
- * directions:
- - should contain a bitmask of the supported slave directions
- (i.e. excluding mem2mem transfers)
-
- * residue_granularity:
- - Granularity of the transfer residue reported to dma_set_residue.
- - This can be either:
- + Descriptor
- -> Your device doesn't support any kind of residue
- reporting. The framework will only know that a particular
- transaction descriptor is done.
- + Segment
- -> Your device is able to report which chunks have been
- transferred
- + Burst
- -> Your device is able to report which burst have been
- transferred
-
- * dev: should hold the pointer to the struct device associated
- to your current driver instance.
-
-Supported transaction types
----------------------------
-
-The next thing you need is to set which transaction types your device
-(and driver) supports.
-
-Our dma_device structure has a field called cap_mask that holds the
-various types of transaction supported, and you need to modify this
-mask using the dma_cap_set function, with various flags depending on
-transaction types you support as an argument.
-
-All those capabilities are defined in the dma_transaction_type enum,
-in include/linux/dmaengine.h
-
-Currently, the types available are:
- * DMA_MEMCPY
- - The device is able to do memory to memory copies
-
- * DMA_XOR
- - The device is able to perform XOR operations on memory areas
- - Used to accelerate XOR intensive tasks, such as RAID5
-
- * DMA_XOR_VAL
- - The device is able to perform parity check using the XOR
- algorithm against a memory buffer.
-
- * DMA_PQ
- - The device is able to perform RAID6 P+Q computations, P being a
- simple XOR, and Q being a Reed-Solomon algorithm.
-
- * DMA_PQ_VAL
- - The device is able to perform parity check using RAID6 P+Q
- algorithm against a memory buffer.
-
- * DMA_INTERRUPT
- - The device is able to trigger a dummy transfer that will
- generate periodic interrupts
- - Used by the client drivers to register a callback that will be
- called on a regular basis through the DMA controller interrupt
-
- * DMA_PRIVATE
- - The devices only supports slave transfers, and as such isn't
- available for async transfers.
-
- * DMA_ASYNC_TX
- - Must not be set by the device, and will be set by the framework
- if needed
- - /* TODO: What is it about? */
-
- * DMA_SLAVE
- - The device can handle device to memory transfers, including
- scatter-gather transfers.
- - While in the mem2mem case we were having two distinct types to
- deal with a single chunk to copy or a collection of them, here,
- we just have a single transaction type that is supposed to
- handle both.
- - If you want to transfer a single contiguous memory buffer,
- simply build a scatter list with only one item.
-
- * DMA_CYCLIC
- - The device can handle cyclic transfers.
- - A cyclic transfer is a transfer where the chunk collection will
- loop over itself, with the last item pointing to the first.
- - It's usually used for audio transfers, where you want to operate
- on a single ring buffer that you will fill with your audio data.
-
- * DMA_INTERLEAVE
- - The device supports interleaved transfer.
- - These transfers can transfer data from a non-contiguous buffer
- to a non-contiguous buffer, opposed to DMA_SLAVE that can
- transfer data from a non-contiguous data set to a continuous
- destination buffer.
- - It's usually used for 2d content transfers, in which case you
- want to transfer a portion of uncompressed data directly to the
- display to print it
-
-These various types will also affect how the source and destination
-addresses change over time.
-
-Addresses pointing to RAM are typically incremented (or decremented)
-after each transfer. In case of a ring buffer, they may loop
-(DMA_CYCLIC). Addresses pointing to a device's register (e.g. a FIFO)
-are typically fixed.
-
-Device operations
------------------
-
-Our dma_device structure also requires a few function pointers in
-order to implement the actual logic, now that we described what
-operations we were able to perform.
-
-The functions that we have to fill in there, and hence have to
-implement, obviously depend on the transaction types you reported as
-supported.
-
- * device_alloc_chan_resources
- * device_free_chan_resources
- - These functions will be called whenever a driver will call
- dma_request_channel or dma_release_channel for the first/last
- time on the channel associated to that driver.
- - They are in charge of allocating/freeing all the needed
- resources in order for that channel to be useful for your
- driver.
- - These functions can sleep.
-
- * device_prep_dma_*
- - These functions are matching the capabilities you registered
- previously.
- - These functions all take the buffer or the scatterlist relevant
- for the transfer being prepared, and should create a hardware
- descriptor or a list of hardware descriptors from it
- - These functions can be called from an interrupt context
- - Any allocation you might do should be using the GFP_NOWAIT
- flag, in order not to potentially sleep, but without depleting
- the emergency pool either.
- - Drivers should try to pre-allocate any memory they might need
- during the transfer setup at probe time to avoid putting to
- much pressure on the nowait allocator.
-
- - It should return a unique instance of the
- dma_async_tx_descriptor structure, that further represents this
- particular transfer.
-
- - This structure can be initialized using the function
- dma_async_tx_descriptor_init.
- - You'll also need to set two fields in this structure:
- + flags:
- TODO: Can it be modified by the driver itself, or
- should it be always the flags passed in the arguments
-
- + tx_submit: A pointer to a function you have to implement,
- that is supposed to push the current
- transaction descriptor to a pending queue, waiting
- for issue_pending to be called.
- - In this structure the function pointer callback_result can be
- initialized in order for the submitter to be notified that a
- transaction has completed. In the earlier code the function pointer
- callback has been used. However it does not provide any status to the
- transaction and will be deprecated. The result structure defined as
- dmaengine_result that is passed in to callback_result has two fields:
- + result: This provides the transfer result defined by
- dmaengine_tx_result. Either success or some error
- condition.
- + residue: Provides the residue bytes of the transfer for those that
- support residue.
-
- * device_issue_pending
- - Takes the first transaction descriptor in the pending queue,
- and starts the transfer. Whenever that transfer is done, it
- should move to the next transaction in the list.
- - This function can be called in an interrupt context
-
- * device_tx_status
- - Should report the bytes left to go over on the given channel
- - Should only care about the transaction descriptor passed as
- argument, not the currently active one on a given channel
- - The tx_state argument might be NULL
- - Should use dma_set_residue to report it
- - In the case of a cyclic transfer, it should only take into
- account the current period.
- - This function can be called in an interrupt context.
-
- * device_config
- - Reconfigures the channel with the configuration given as
- argument
- - This command should NOT perform synchronously, or on any
- currently queued transfers, but only on subsequent ones
- - In this case, the function will receive a dma_slave_config
- structure pointer as an argument, that will detail which
- configuration to use.
- - Even though that structure contains a direction field, this
- field is deprecated in favor of the direction argument given to
- the prep_* functions
- - This call is mandatory for slave operations only. This should NOT be
- set or expected to be set for memcpy operations.
- If a driver support both, it should use this call for slave
- operations only and not for memcpy ones.
-
- * device_pause
- - Pauses a transfer on the channel
- - This command should operate synchronously on the channel,
- pausing right away the work of the given channel
-
- * device_resume
- - Resumes a transfer on the channel
- - This command should operate synchronously on the channel,
- resuming right away the work of the given channel
-
- * device_terminate_all
- - Aborts all the pending and ongoing transfers on the channel
- - For aborted transfers the complete callback should not be called
- - Can be called from atomic context or from within a complete
- callback of a descriptor. Must not sleep. Drivers must be able
- to handle this correctly.
- - Termination may be asynchronous. The driver does not have to
- wait until the currently active transfer has completely stopped.
- See device_synchronize.
-
- * device_synchronize
- - Must synchronize the termination of a channel to the current
- context.
- - Must make sure that memory for previously submitted
- descriptors is no longer accessed by the DMA controller.
- - Must make sure that all complete callbacks for previously
- submitted descriptors have finished running and none are
- scheduled to run.
- - May sleep.
-
-
-Misc notes (stuff that should be documented, but don't really know
-where to put them)
-------------------------------------------------------------------
- * dma_run_dependencies
- - Should be called at the end of an async TX transfer, and can be
- ignored in the slave transfers case.
- - Makes sure that dependent operations are run before marking it
- as complete.
-
- * dma_cookie_t
- - it's a DMA transaction ID that will increment over time.
- - Not really relevant any more since the introduction of virt-dma
- that abstracts it away.
-
- * DMA_CTRL_ACK
- - If clear, the descriptor cannot be reused by provider until the
- client acknowledges receipt, i.e. has has a chance to establish any
- dependency chains
- - This can be acked by invoking async_tx_ack()
- - If set, does not mean descriptor can be reused
-
- * DMA_CTRL_REUSE
- - If set, the descriptor can be reused after being completed. It should
- not be freed by provider if this flag is set.
- - The descriptor should be prepared for reuse by invoking
- dmaengine_desc_set_reuse() which will set DMA_CTRL_REUSE.
- - dmaengine_desc_set_reuse() will succeed only when channel support
- reusable descriptor as exhibited by capabilities
- - As a consequence, if a device driver wants to skip the dma_map_sg() and
- dma_unmap_sg() in between 2 transfers, because the DMA'd data wasn't used,
- it can resubmit the transfer right after its completion.
- - Descriptor can be freed in few ways
- - Clearing DMA_CTRL_REUSE by invoking dmaengine_desc_clear_reuse()
- and submitting for last txn
- - Explicitly invoking dmaengine_desc_free(), this can succeed only
- when DMA_CTRL_REUSE is already set
- - Terminating the channel
-
- * DMA_PREP_CMD
- - If set, the client driver tells DMA controller that passed data in DMA
- API is command data.
- - Interpretation of command data is DMA controller specific. It can be
- used for issuing commands to other peripherals/register reads/register
- writes for which the descriptor should be in different format from
- normal data descriptors.
-
-General Design Notes
---------------------
-
-Most of the DMAEngine drivers you'll see are based on a similar design
-that handles the end of transfer interrupts in the handler, but defer
-most work to a tasklet, including the start of a new transfer whenever
-the previous transfer ended.
-
-This is a rather inefficient design though, because the inter-transfer
-latency will be not only the interrupt latency, but also the
-scheduling latency of the tasklet, which will leave the channel idle
-in between, which will slow down the global transfer rate.
-
-You should avoid this kind of practice, and instead of electing a new
-transfer in your tasklet, move that part to the interrupt handler in
-order to have a shorter idle window (that we can't really avoid
-anyway).
-
-Glossary
---------
-
-Burst: A number of consecutive read or write operations
- that can be queued to buffers before being flushed to
- memory.
-Chunk: A contiguous collection of bursts
-Transfer: A collection of chunks (be it contiguous or not)
+++ /dev/null
-PXA/MMP - DMA Slave controller
-==============================
-
-Constraints
------------
- a) Transfers hot queuing
- A driver submitting a transfer and issuing it should be granted the transfer
- is queued even on a running DMA channel.
- This implies that the queuing doesn't wait for the previous transfer end,
- and that the descriptor chaining is not only done in the irq/tasklet code
- triggered by the end of the transfer.
- A transfer which is submitted and issued on a phy doesn't wait for a phy to
- stop and restart, but is submitted on a "running channel". The other
- drivers, especially mmp_pdma waited for the phy to stop before relaunching
- a new transfer.
-
- b) All transfers having asked for confirmation should be signaled
- Any issued transfer with DMA_PREP_INTERRUPT should trigger a callback call.
- This implies that even if an irq/tasklet is triggered by end of tx1, but
- at the time of irq/dma tx2 is already finished, tx1->complete() and
- tx2->complete() should be called.
-
- c) Channel running state
- A driver should be able to query if a channel is running or not. For the
- multimedia case, such as video capture, if a transfer is submitted and then
- a check of the DMA channel reports a "stopped channel", the transfer should
- not be issued until the next "start of frame interrupt", hence the need to
- know if a channel is in running or stopped state.
-
- d) Bandwidth guarantee
- The PXA architecture has 4 levels of DMAs priorities : high, normal, low.
- The high priorities get twice as much bandwidth as the normal, which get twice
- as much as the low priorities.
- A driver should be able to request a priority, especially the real-time
- ones such as pxa_camera with (big) throughputs.
-
-Design
-------
- a) Virtual channels
- Same concept as in sa11x0 driver, ie. a driver was assigned a "virtual
- channel" linked to the requestor line, and the physical DMA channel is
- assigned on the fly when the transfer is issued.
-
- b) Transfer anatomy for a scatter-gather transfer
- +------------+-----+---------------+----------------+-----------------+
- | desc-sg[0] | ... | desc-sg[last] | status updater | finisher/linker |
- +------------+-----+---------------+----------------+-----------------+
-
- This structure is pointed by dma->sg_cpu.
- The descriptors are used as follows :
- - desc-sg[i]: i-th descriptor, transferring the i-th sg
- element to the video buffer scatter gather
- - status updater
- Transfers a single u32 to a well known dma coherent memory to leave
- a trace that this transfer is done. The "well known" is unique per
- physical channel, meaning that a read of this value will tell which
- is the last finished transfer at that point in time.
- - finisher: has ddadr=DADDR_STOP, dcmd=ENDIRQEN
- - linker: has ddadr= desc-sg[0] of next transfer, dcmd=0
-
- c) Transfers hot-chaining
- Suppose the running chain is :
- Buffer 1 Buffer 2
- +---------+----+---+ +----+----+----+---+
- | d0 | .. | dN | l | | d0 | .. | dN | f |
- +---------+----+-|-+ ^----+----+----+---+
- | |
- +----+
-
- After a call to dmaengine_submit(b3), the chain will look like :
- Buffer 1 Buffer 2 Buffer 3
- +---------+----+---+ +----+----+----+---+ +----+----+----+---+
- | d0 | .. | dN | l | | d0 | .. | dN | l | | d0 | .. | dN | f |
- +---------+----+-|-+ ^----+----+----+-|-+ ^----+----+----+---+
- | | | |
- +----+ +----+
- new_link
-
- If while new_link was created the DMA channel stopped, it is _not_
- restarted. Hot-chaining doesn't break the assumption that
- dma_async_issue_pending() is to be used to ensure the transfer is actually started.
-
- One exception to this rule :
- - if Buffer1 and Buffer2 had all their addresses 8 bytes aligned
- - and if Buffer3 has at least one address not 4 bytes aligned
- - then hot-chaining cannot happen, as the channel must be stopped, the
- "align bit" must be set, and the channel restarted As a consequence,
- such a transfer tx_submit() will be queued on the submitted queue, and
- this specific case if the DMA is already running in aligned mode.
-
- d) Transfers completion updater
- Each time a transfer is completed on a channel, an interrupt might be
- generated or not, up to the client's request. But in each case, the last
- descriptor of a transfer, the "status updater", will write the latest
- transfer being completed into the physical channel's completion mark.
-
- This will speed up residue calculation, for large transfers such as video
- buffers which hold around 6k descriptors or more. This also allows without
- any lock to find out what is the latest completed transfer in a running
- DMA chain.
-
- e) Transfers completion, irq and tasklet
- When a transfer flagged as "DMA_PREP_INTERRUPT" is finished, the dma irq
- is raised. Upon this interrupt, a tasklet is scheduled for the physical
- channel.
- The tasklet is responsible for :
- - reading the physical channel last updater mark
- - calling all the transfer callbacks of finished transfers, based on
- that mark, and each transfer flags.
- If a transfer is completed while this handling is done, a dma irq will
- be raised, and the tasklet will be scheduled once again, having a new
- updater mark.
-
- f) Residue
- Residue granularity will be descriptor based. The issued but not completed
- transfers will be scanned for all of their descriptors against the
- currently running descriptor.
-
- g) Most complicated case of driver's tx queues
- The most tricky situation is when :
- - there are not "acked" transfers (tx0)
- - a driver submitted an aligned tx1, not chained
- - a driver submitted an aligned tx2 => tx2 is cold chained to tx1
- - a driver issued tx1+tx2 => channel is running in aligned mode
- - a driver submitted an aligned tx3 => tx3 is hot-chained
- - a driver submitted an unaligned tx4 => tx4 is put in submitted queue,
- not chained
- - a driver issued tx4 => tx4 is put in issued queue, not chained
- - a driver submitted an aligned tx5 => tx5 is put in submitted queue, not
- chained
- - a driver submitted an aligned tx6 => tx6 is put in submitted queue,
- cold chained to tx5
-
- This translates into (after tx4 is issued) :
- - issued queue
- +-----+ +-----+ +-----+ +-----+
- | tx1 | | tx2 | | tx3 | | tx4 |
- +---|-+ ^---|-+ ^-----+ +-----+
- | | | |
- +---+ +---+
- - submitted queue
- +-----+ +-----+
- | tx5 | | tx6 |
- +---|-+ ^-----+
- | |
- +---+
- - completed queue : empty
- - allocated queue : tx0
-
- It should be noted that after tx3 is completed, the channel is stopped, and
- restarted in "unaligned mode" to handle tx4.
-
-Author: Robert Jarzmik <robert.jarzmik@free.fr>
from the source file.
The kernel-doc extension is included in the kernel source tree, at
-``Documentation/sphinx/kernel-doc.py``. Internally, it uses the
+``Documentation/sphinx/kerneldoc.py``. Internally, it uses the
``scripts/kernel-doc`` script to extract the documentation comments from the
source.
--- /dev/null
+====================
+DMA Engine API Guide
+====================
+
+Vinod Koul <vinod dot koul at intel.com>
+
+.. note:: For DMA Engine usage in async_tx please see:
+ ``Documentation/crypto/async-tx-api.txt``
+
+
+Below is a guide to device driver writers on how to use the Slave-DMA API of the
+DMA Engine. This is applicable only for slave DMA usage only.
+
+DMA usage
+=========
+
+The slave DMA usage consists of following steps:
+
+- Allocate a DMA slave channel
+
+- Set slave and controller specific parameters
+
+- Get a descriptor for transaction
+
+- Submit the transaction
+
+- Issue pending requests and wait for callback notification
+
+The details of these operations are:
+
+1. Allocate a DMA slave channel
+
+ Channel allocation is slightly different in the slave DMA context,
+ client drivers typically need a channel from a particular DMA
+ controller only and even in some cases a specific channel is desired.
+ To request a channel dma_request_chan() API is used.
+
+ Interface:
+
+ .. code-block:: c
+
+ struct dma_chan *dma_request_chan(struct device *dev, const char *name);
+
+ Which will find and return the ``name`` DMA channel associated with the 'dev'
+ device. The association is done via DT, ACPI or board file based
+ dma_slave_map matching table.
+
+ A channel allocated via this interface is exclusive to the caller,
+ until dma_release_channel() is called.
+
+2. Set slave and controller specific parameters
+
+ Next step is always to pass some specific information to the DMA
+ driver. Most of the generic information which a slave DMA can use
+ is in struct dma_slave_config. This allows the clients to specify
+ DMA direction, DMA addresses, bus widths, DMA burst lengths etc
+ for the peripheral.
+
+ If some DMA controllers have more parameters to be sent then they
+ should try to embed struct dma_slave_config in their controller
+ specific structure. That gives flexibility to client to pass more
+ parameters, if required.
+
+ Interface:
+
+ .. code-block:: c
+
+ int dmaengine_slave_config(struct dma_chan *chan,
+ struct dma_slave_config *config)
+
+ Please see the dma_slave_config structure definition in dmaengine.h
+ for a detailed explanation of the struct members. Please note
+ that the 'direction' member will be going away as it duplicates the
+ direction given in the prepare call.
+
+3. Get a descriptor for transaction
+
+ For slave usage the various modes of slave transfers supported by the
+ DMA-engine are:
+
+ - slave_sg: DMA a list of scatter gather buffers from/to a peripheral
+
+ - dma_cyclic: Perform a cyclic DMA operation from/to a peripheral till the
+ operation is explicitly stopped.
+
+ - interleaved_dma: This is common to Slave as well as M2M clients. For slave
+ address of devices' fifo could be already known to the driver.
+ Various types of operations could be expressed by setting
+ appropriate values to the 'dma_interleaved_template' members.
+
+ A non-NULL return of this transfer API represents a "descriptor" for
+ the given transaction.
+
+ Interface:
+
+ .. code-block:: c
+
+ struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
+ struct dma_chan *chan, struct scatterlist *sgl,
+ unsigned int sg_len, enum dma_data_direction direction,
+ unsigned long flags);
+
+ struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
+ struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
+ size_t period_len, enum dma_data_direction direction);
+
+ struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
+ struct dma_chan *chan, struct dma_interleaved_template *xt,
+ unsigned long flags);
+
+ The peripheral driver is expected to have mapped the scatterlist for
+ the DMA operation prior to calling dmaengine_prep_slave_sg(), and must
+ keep the scatterlist mapped until the DMA operation has completed.
+ The scatterlist must be mapped using the DMA struct device.
+ If a mapping needs to be synchronized later, dma_sync_*_for_*() must be
+ called using the DMA struct device, too.
+ So, normal setup should look like this:
+
+ .. code-block:: c
+
+ nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
+ if (nr_sg == 0)
+ /* error */
+
+ desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
+
+ Once a descriptor has been obtained, the callback information can be
+ added and the descriptor must then be submitted. Some DMA engine
+ drivers may hold a spinlock between a successful preparation and
+ submission so it is important that these two operations are closely
+ paired.
+
+ .. note::
+
+ Although the async_tx API specifies that completion callback
+ routines cannot submit any new operations, this is not the
+ case for slave/cyclic DMA.
+
+ For slave DMA, the subsequent transaction may not be available
+ for submission prior to callback function being invoked, so
+ slave DMA callbacks are permitted to prepare and submit a new
+ transaction.
+
+ For cyclic DMA, a callback function may wish to terminate the
+ DMA via dmaengine_terminate_async().
+
+ Therefore, it is important that DMA engine drivers drop any
+ locks before calling the callback function which may cause a
+ deadlock.
+
+ Note that callbacks will always be invoked from the DMA
+ engines tasklet, never from interrupt context.
+
+4. Submit the transaction
+
+ Once the descriptor has been prepared and the callback information
+ added, it must be placed on the DMA engine drivers pending queue.
+
+ Interface:
+
+ .. code-block:: c
+
+ dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
+
+ This returns a cookie can be used to check the progress of DMA engine
+ activity via other DMA engine calls not covered in this document.
+
+ dmaengine_submit() will not start the DMA operation, it merely adds
+ it to the pending queue. For this, see step 5, dma_async_issue_pending.
+
+5. Issue pending DMA requests and wait for callback notification
+
+ The transactions in the pending queue can be activated by calling the
+ issue_pending API. If channel is idle then the first transaction in
+ queue is started and subsequent ones queued up.
+
+ On completion of each DMA operation, the next in queue is started and
+ a tasklet triggered. The tasklet will then call the client driver
+ completion callback routine for notification, if set.
+
+ Interface:
+
+ .. code-block:: c
+
+ void dma_async_issue_pending(struct dma_chan *chan);
+
+Further APIs:
+------------
+
+1. Terminate APIs
+
+ .. code-block:: c
+
+ int dmaengine_terminate_sync(struct dma_chan *chan)
+ int dmaengine_terminate_async(struct dma_chan *chan)
+ int dmaengine_terminate_all(struct dma_chan *chan) /* DEPRECATED */
+
+ This causes all activity for the DMA channel to be stopped, and may
+ discard data in the DMA FIFO which hasn't been fully transferred.
+ No callback functions will be called for any incomplete transfers.
+
+ Two variants of this function are available.
+
+ dmaengine_terminate_async() might not wait until the DMA has been fully
+ stopped or until any running complete callbacks have finished. But it is
+ possible to call dmaengine_terminate_async() from atomic context or from
+ within a complete callback. dmaengine_synchronize() must be called before it
+ is safe to free the memory accessed by the DMA transfer or free resources
+ accessed from within the complete callback.
+
+ dmaengine_terminate_sync() will wait for the transfer and any running
+ complete callbacks to finish before it returns. But the function must not be
+ called from atomic context or from within a complete callback.
+
+ dmaengine_terminate_all() is deprecated and should not be used in new code.
+
+2. Pause API
+
+ .. code-block:: c
+
+ int dmaengine_pause(struct dma_chan *chan)
+
+ This pauses activity on the DMA channel without data loss.
+
+3. Resume API
+
+ .. code-block:: c
+
+ int dmaengine_resume(struct dma_chan *chan)
+
+ Resume a previously paused DMA channel. It is invalid to resume a
+ channel which is not currently paused.
+
+4. Check Txn complete
+
+ .. code-block:: c
+
+ enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
+ dma_cookie_t cookie, dma_cookie_t *last, dma_cookie_t *used)
+
+ This can be used to check the status of the channel. Please see
+ the documentation in include/linux/dmaengine.h for a more complete
+ description of this API.
+
+ This can be used in conjunction with dma_async_is_complete() and
+ the cookie returned from dmaengine_submit() to check for
+ completion of a specific DMA transaction.
+
+ .. note::
+
+ Not all DMA engine drivers can return reliable information for
+ a running DMA channel. It is recommended that DMA engine users
+ pause or stop (via dmaengine_terminate_all()) the channel before
+ using this API.
+
+5. Synchronize termination API
+
+ .. code-block:: c
+
+ void dmaengine_synchronize(struct dma_chan *chan)
+
+ Synchronize the termination of the DMA channel to the current context.
+
+ This function should be used after dmaengine_terminate_async() to synchronize
+ the termination of the DMA channel to the current context. The function will
+ wait for the transfer and any running complete callbacks to finish before it
+ returns.
+
+ If dmaengine_terminate_async() is used to stop the DMA channel this function
+ must be called before it is safe to free memory accessed by previously
+ submitted descriptors or to free any resources accessed within the complete
+ callback of previously submitted descriptors.
+
+ The behavior of this function is undefined if dma_async_issue_pending() has
+ been called between dmaengine_terminate_async() and this function.
- DMA Test Guide
- ==============
+==============
+DMA Test Guide
+==============
-
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+Andy Shevchenko <andriy.shevchenko@linux.intel.com>
This small document introduces how to test DMA drivers using dmatest module.
- Part 1 - How to build the test module
+Part 1 - How to build the test module
+=====================================
The menuconfig contains an option that could be found by following path:
Device Drivers -> DMA Engine support -> DMA Test client
In the configuration file the option called CONFIG_DMATEST. The dmatest could
be built as module or inside kernel. Let's consider those cases.
- Part 2 - When dmatest is built as a module...
+Part 2 - When dmatest is built as a module
+==========================================
-Example of usage:
- % modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
+Example of usage: ::
-...or:
- % modprobe dmatest
- % echo dma0chan0 > /sys/module/dmatest/parameters/channel
- % echo 2000 > /sys/module/dmatest/parameters/timeout
- % echo 1 > /sys/module/dmatest/parameters/iterations
- % echo 1 > /sys/module/dmatest/parameters/run
+ % modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
-...or on the kernel command line:
+...or: ::
- dmatest.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
+ % modprobe dmatest
+ % echo dma0chan0 > /sys/module/dmatest/parameters/channel
+ % echo 2000 > /sys/module/dmatest/parameters/timeout
+ % echo 1 > /sys/module/dmatest/parameters/iterations
+ % echo 1 > /sys/module/dmatest/parameters/run
-Hint: available channel list could be extracted by running the following
-command:
- % ls -1 /sys/class/dma/
+...or on the kernel command line: ::
+
+ dmatest.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
+
+..hint:: available channel list could be extracted by running the following
+ command:
+
+::
+
+ % ls -1 /sys/class/dma/
Once started a message like "dmatest: Started 1 threads using dma0chan0" is
emitted. After that only test failure messages are reported until the test
Note that running a new test will not stop any in progress test.
-The following command returns the state of the test.
- % cat /sys/module/dmatest/parameters/run
+The following command returns the state of the test. ::
+
+ % cat /sys/module/dmatest/parameters/run
To wait for test completion userpace can poll 'run' until it is false, or use
the wait parameter. Specifying 'wait=1' when loading the module causes module
to complete before exiting. Note that if 'iterations' is set to 'infinite' then
waiting is disabled.
-Example:
- % modprobe dmatest run=1 iterations=42 wait=1
- % modprobe -r dmatest
-...or:
- % modprobe dmatest run=1 iterations=42
- % cat /sys/module/dmatest/parameters/wait
- % modprobe -r dmatest
+Example: ::
+
+ % modprobe dmatest run=1 iterations=42 wait=1
+ % modprobe -r dmatest
- Part 3 - When built-in in the kernel...
+...or: ::
+
+ % modprobe dmatest run=1 iterations=42
+ % cat /sys/module/dmatest/parameters/wait
+ % modprobe -r dmatest
+
+Part 3 - When built-in in the kernel
+====================================
The module parameters that is supplied to the kernel command line will be used
for the first performed test. After user gets a control, the test could be
section "Part 2 - When dmatest is built as a module..."
In both cases the module parameters are used as the actual values for the test
-case. You always could check them at run-time by running
- % grep -H . /sys/module/dmatest/parameters/*
+case. You always could check them at run-time by running ::
+
+ % grep -H . /sys/module/dmatest/parameters/*
- Part 4 - Gathering the test results
+Part 4 - Gathering the test results
+===================================
-Test results are printed to the kernel log buffer with the format:
+Test results are printed to the kernel log buffer with the format: ::
-"dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
+ "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
-Example of output:
- % dmesg | tail -n 1
- dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
+Example of output: ::
+
+
+ % dmesg | tail -n 1
+ dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
The message format is unified across the different types of errors. A number in
the parens represents additional information, e.g. error code, error counter,
or status. A test thread also emits a summary line at completion listing the
number of tests executed, number that failed, and a result code.
-Example:
- % dmesg | tail -n 1
- dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
+Example: ::
+
+ % dmesg | tail -n 1
+ dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
The details of a data miscompare error are also emitted, but do not follow the
above format.
--- /dev/null
+=======================
+DMAEngine documentation
+=======================
+
+DMAEngine documentation provides documents for various aspects of DMAEngine
+framework.
+
+DMAEngine documentation
+-----------------------
+
+This book helps with DMAengine internal APIs and guide for DMAEngine device
+driver writers.
+
+.. toctree::
+ :maxdepth: 1
+
+ provider
+
+DMAEngine client documentation
+------------------------------
+
+This book is a guide to device driver writers on how to use the Slave-DMA
+API of the DMAEngine. This is applicable only for slave DMA usage only.
+
+.. toctree::
+ :maxdepth: 1
+
+ client
+
+DMA Test documentation
+----------------------
+
+This book introduces how to test DMA drivers using dmatest module.
+
+.. toctree::
+ :maxdepth: 1
+
+ dmatest
+
+PXA DMA documentation
+----------------------
+
+This book adds some notes about PXA DMA
+
+.. toctree::
+ :maxdepth: 1
+
+ pxa_dma
+
+.. only:: subproject
+
+ Indices
+ =======
+
+ * :ref:`genindex`
--- /dev/null
+==================================
+DMAengine controller documentation
+==================================
+
+Hardware Introduction
+=====================
+
+Most of the Slave DMA controllers have the same general principles of
+operations.
+
+They have a given number of channels to use for the DMA transfers, and
+a given number of requests lines.
+
+Requests and channels are pretty much orthogonal. Channels can be used
+to serve several to any requests. To simplify, channels are the
+entities that will be doing the copy, and requests what endpoints are
+involved.
+
+The request lines actually correspond to physical lines going from the
+DMA-eligible devices to the controller itself. Whenever the device
+will want to start a transfer, it will assert a DMA request (DRQ) by
+asserting that request line.
+
+A very simple DMA controller would only take into account a single
+parameter: the transfer size. At each clock cycle, it would transfer a
+byte of data from one buffer to another, until the transfer size has
+been reached.
+
+That wouldn't work well in the real world, since slave devices might
+require a specific number of bits to be transferred in a single
+cycle. For example, we may want to transfer as much data as the
+physical bus allows to maximize performances when doing a simple
+memory copy operation, but our audio device could have a narrower FIFO
+that requires data to be written exactly 16 or 24 bits at a time. This
+is why most if not all of the DMA controllers can adjust this, using a
+parameter called the transfer width.
+
+Moreover, some DMA controllers, whenever the RAM is used as a source
+or destination, can group the reads or writes in memory into a buffer,
+so instead of having a lot of small memory accesses, which is not
+really efficient, you'll get several bigger transfers. This is done
+using a parameter called the burst size, that defines how many single
+reads/writes it's allowed to do without the controller splitting the
+transfer into smaller sub-transfers.
+
+Our theoretical DMA controller would then only be able to do transfers
+that involve a single contiguous block of data. However, some of the
+transfers we usually have are not, and want to copy data from
+non-contiguous buffers to a contiguous buffer, which is called
+scatter-gather.
+
+DMAEngine, at least for mem2dev transfers, require support for
+scatter-gather. So we're left with two cases here: either we have a
+quite simple DMA controller that doesn't support it, and we'll have to
+implement it in software, or we have a more advanced DMA controller,
+that implements in hardware scatter-gather.
+
+The latter are usually programmed using a collection of chunks to
+transfer, and whenever the transfer is started, the controller will go
+over that collection, doing whatever we programmed there.
+
+This collection is usually either a table or a linked list. You will
+then push either the address of the table and its number of elements,
+or the first item of the list to one channel of the DMA controller,
+and whenever a DRQ will be asserted, it will go through the collection
+to know where to fetch the data from.
+
+Either way, the format of this collection is completely dependent on
+your hardware. Each DMA controller will require a different structure,
+but all of them will require, for every chunk, at least the source and
+destination addresses, whether it should increment these addresses or
+not and the three parameters we saw earlier: the burst size, the
+transfer width and the transfer size.
+
+The one last thing is that usually, slave devices won't issue DRQ by
+default, and you have to enable this in your slave device driver first
+whenever you're willing to use DMA.
+
+These were just the general memory-to-memory (also called mem2mem) or
+memory-to-device (mem2dev) kind of transfers. Most devices often
+support other kind of transfers or memory operations that dmaengine
+support and will be detailed later in this document.
+
+DMA Support in Linux
+====================
+
+Historically, DMA controller drivers have been implemented using the
+async TX API, to offload operations such as memory copy, XOR,
+cryptography, etc., basically any memory to memory operation.
+
+Over time, the need for memory to device transfers arose, and
+dmaengine was extended. Nowadays, the async TX API is written as a
+layer on top of dmaengine, and acts as a client. Still, dmaengine
+accommodates that API in some cases, and made some design choices to
+ensure that it stayed compatible.
+
+For more information on the Async TX API, please look the relevant
+documentation file in Documentation/crypto/async-tx-api.txt.
+
+DMAEngine APIs
+==============
+
+``struct dma_device`` Initialization
+------------------------------------
+
+Just like any other kernel framework, the whole DMAEngine registration
+relies on the driver filling a structure and registering against the
+framework. In our case, that structure is dma_device.
+
+The first thing you need to do in your driver is to allocate this
+structure. Any of the usual memory allocators will do, but you'll also
+need to initialize a few fields in there:
+
+- channels: should be initialized as a list using the
+ INIT_LIST_HEAD macro for example
+
+- src_addr_widths:
+ should contain a bitmask of the supported source transfer width
+
+- dst_addr_widths:
+ should contain a bitmask of the supported destination transfer width
+
+- directions:
+ should contain a bitmask of the supported slave directions
+ (i.e. excluding mem2mem transfers)
+
+- residue_granularity:
+
+ - Granularity of the transfer residue reported to dma_set_residue.
+ This can be either:
+
+ - Descriptor
+
+ - Your device doesn't support any kind of residue
+ reporting. The framework will only know that a particular
+ transaction descriptor is done.
+
+ - Segment
+
+ - Your device is able to report which chunks have been transferred
+
+ - Burst
+
+ - Your device is able to report which burst have been transferred
+
+ - dev: should hold the pointer to the ``struct device`` associated
+ to your current driver instance.
+
+Supported transaction types
+---------------------------
+
+The next thing you need is to set which transaction types your device
+(and driver) supports.
+
+Our ``dma_device structure`` has a field called cap_mask that holds the
+various types of transaction supported, and you need to modify this
+mask using the dma_cap_set function, with various flags depending on
+transaction types you support as an argument.
+
+All those capabilities are defined in the ``dma_transaction_type enum``,
+in ``include/linux/dmaengine.h``
+
+Currently, the types available are:
+
+- DMA_MEMCPY
+
+ - The device is able to do memory to memory copies
+
+- DMA_XOR
+
+ - The device is able to perform XOR operations on memory areas
+
+ - Used to accelerate XOR intensive tasks, such as RAID5
+
+- DMA_XOR_VAL
+
+ - The device is able to perform parity check using the XOR
+ algorithm against a memory buffer.
+
+- DMA_PQ
+
+ - The device is able to perform RAID6 P+Q computations, P being a
+ simple XOR, and Q being a Reed-Solomon algorithm.
+
+- DMA_PQ_VAL
+
+ - The device is able to perform parity check using RAID6 P+Q
+ algorithm against a memory buffer.
+
+- DMA_INTERRUPT
+
+ - The device is able to trigger a dummy transfer that will
+ generate periodic interrupts
+
+ - Used by the client drivers to register a callback that will be
+ called on a regular basis through the DMA controller interrupt
+
+- DMA_PRIVATE
+
+ - The devices only supports slave transfers, and as such isn't
+ available for async transfers.
+
+- DMA_ASYNC_TX
+
+ - Must not be set by the device, and will be set by the framework
+ if needed
+
+ - TODO: What is it about?
+
+- DMA_SLAVE
+
+ - The device can handle device to memory transfers, including
+ scatter-gather transfers.
+
+ - While in the mem2mem case we were having two distinct types to
+ deal with a single chunk to copy or a collection of them, here,
+ we just have a single transaction type that is supposed to
+ handle both.
+
+ - If you want to transfer a single contiguous memory buffer,
+ simply build a scatter list with only one item.
+
+- DMA_CYCLIC
+
+ - The device can handle cyclic transfers.
+
+ - A cyclic transfer is a transfer where the chunk collection will
+ loop over itself, with the last item pointing to the first.
+
+ - It's usually used for audio transfers, where you want to operate
+ on a single ring buffer that you will fill with your audio data.
+
+- DMA_INTERLEAVE
+
+ - The device supports interleaved transfer.
+
+ - These transfers can transfer data from a non-contiguous buffer
+ to a non-contiguous buffer, opposed to DMA_SLAVE that can
+ transfer data from a non-contiguous data set to a continuous
+ destination buffer.
+
+ - It's usually used for 2d content transfers, in which case you
+ want to transfer a portion of uncompressed data directly to the
+ display to print it
+
+These various types will also affect how the source and destination
+addresses change over time.
+
+Addresses pointing to RAM are typically incremented (or decremented)
+after each transfer. In case of a ring buffer, they may loop
+(DMA_CYCLIC). Addresses pointing to a device's register (e.g. a FIFO)
+are typically fixed.
+
+Device operations
+-----------------
+
+Our dma_device structure also requires a few function pointers in
+order to implement the actual logic, now that we described what
+operations we were able to perform.
+
+The functions that we have to fill in there, and hence have to
+implement, obviously depend on the transaction types you reported as
+supported.
+
+- ``device_alloc_chan_resources``
+
+- ``device_free_chan_resources``
+
+ - These functions will be called whenever a driver will call
+ ``dma_request_channel`` or ``dma_release_channel`` for the first/last
+ time on the channel associated to that driver.
+
+ - They are in charge of allocating/freeing all the needed
+ resources in order for that channel to be useful for your driver.
+
+ - These functions can sleep.
+
+- ``device_prep_dma_*``
+
+ - These functions are matching the capabilities you registered
+ previously.
+
+ - These functions all take the buffer or the scatterlist relevant
+ for the transfer being prepared, and should create a hardware
+ descriptor or a list of hardware descriptors from it
+
+ - These functions can be called from an interrupt context
+
+ - Any allocation you might do should be using the GFP_NOWAIT
+ flag, in order not to potentially sleep, but without depleting
+ the emergency pool either.
+
+ - Drivers should try to pre-allocate any memory they might need
+ during the transfer setup at probe time to avoid putting to
+ much pressure on the nowait allocator.
+
+ - It should return a unique instance of the
+ ``dma_async_tx_descriptor structure``, that further represents this
+ particular transfer.
+
+ - This structure can be initialized using the function
+ ``dma_async_tx_descriptor_init``.
+
+ - You'll also need to set two fields in this structure:
+
+ - flags:
+ TODO: Can it be modified by the driver itself, or
+ should it be always the flags passed in the arguments
+
+ - tx_submit: A pointer to a function you have to implement,
+ that is supposed to push the current transaction descriptor to a
+ pending queue, waiting for issue_pending to be called.
+
+ - In this structure the function pointer callback_result can be
+ initialized in order for the submitter to be notified that a
+ transaction has completed. In the earlier code the function pointer
+ callback has been used. However it does not provide any status to the
+ transaction and will be deprecated. The result structure defined as
+ ``dmaengine_result`` that is passed in to callback_result
+ has two fields:
+
+ - result: This provides the transfer result defined by
+ ``dmaengine_tx_result``. Either success or some error condition.
+
+ - residue: Provides the residue bytes of the transfer for those that
+ support residue.
+
+- ``device_issue_pending``
+
+ - Takes the first transaction descriptor in the pending queue,
+ and starts the transfer. Whenever that transfer is done, it
+ should move to the next transaction in the list.
+
+ - This function can be called in an interrupt context
+
+- ``device_tx_status``
+
+ - Should report the bytes left to go over on the given channel
+
+ - Should only care about the transaction descriptor passed as
+ argument, not the currently active one on a given channel
+
+ - The tx_state argument might be NULL
+
+ - Should use dma_set_residue to report it
+
+ - In the case of a cyclic transfer, it should only take into
+ account the current period.
+
+ - This function can be called in an interrupt context.
+
+- device_config
+
+ - Reconfigures the channel with the configuration given as argument
+
+ - This command should NOT perform synchronously, or on any
+ currently queued transfers, but only on subsequent ones
+
+ - In this case, the function will receive a ``dma_slave_config``
+ structure pointer as an argument, that will detail which
+ configuration to use.
+
+ - Even though that structure contains a direction field, this
+ field is deprecated in favor of the direction argument given to
+ the prep_* functions
+
+ - This call is mandatory for slave operations only. This should NOT be
+ set or expected to be set for memcpy operations.
+ If a driver support both, it should use this call for slave
+ operations only and not for memcpy ones.
+
+- device_pause
+
+ - Pauses a transfer on the channel
+
+ - This command should operate synchronously on the channel,
+ pausing right away the work of the given channel
+
+- device_resume
+
+ - Resumes a transfer on the channel
+
+ - This command should operate synchronously on the channel,
+ resuming right away the work of the given channel
+
+- device_terminate_all
+
+ - Aborts all the pending and ongoing transfers on the channel
+
+ - For aborted transfers the complete callback should not be called
+
+ - Can be called from atomic context or from within a complete
+ callback of a descriptor. Must not sleep. Drivers must be able
+ to handle this correctly.
+
+ - Termination may be asynchronous. The driver does not have to
+ wait until the currently active transfer has completely stopped.
+ See device_synchronize.
+
+- device_synchronize
+
+ - Must synchronize the termination of a channel to the current
+ context.
+
+ - Must make sure that memory for previously submitted
+ descriptors is no longer accessed by the DMA controller.
+
+ - Must make sure that all complete callbacks for previously
+ submitted descriptors have finished running and none are
+ scheduled to run.
+
+ - May sleep.
+
+
+Misc notes
+==========
+
+(stuff that should be documented, but don't really know
+where to put them)
+
+``dma_run_dependencies``
+
+- Should be called at the end of an async TX transfer, and can be
+ ignored in the slave transfers case.
+
+- Makes sure that dependent operations are run before marking it
+ as complete.
+
+dma_cookie_t
+
+- it's a DMA transaction ID that will increment over time.
+
+- Not really relevant any more since the introduction of ``virt-dma``
+ that abstracts it away.
+
+DMA_CTRL_ACK
+
+- If clear, the descriptor cannot be reused by provider until the
+ client acknowledges receipt, i.e. has has a chance to establish any
+ dependency chains
+
+- This can be acked by invoking async_tx_ack()
+
+- If set, does not mean descriptor can be reused
+
+DMA_CTRL_REUSE
+
+- If set, the descriptor can be reused after being completed. It should
+ not be freed by provider if this flag is set.
+
+- The descriptor should be prepared for reuse by invoking
+ ``dmaengine_desc_set_reuse()`` which will set DMA_CTRL_REUSE.
+
+- ``dmaengine_desc_set_reuse()`` will succeed only when channel support
+ reusable descriptor as exhibited by capabilities
+
+- As a consequence, if a device driver wants to skip the
+ ``dma_map_sg()`` and ``dma_unmap_sg()`` in between 2 transfers,
+ because the DMA'd data wasn't used, it can resubmit the transfer right after
+ its completion.
+
+- Descriptor can be freed in few ways
+
+ - Clearing DMA_CTRL_REUSE by invoking
+ ``dmaengine_desc_clear_reuse()`` and submitting for last txn
+
+ - Explicitly invoking ``dmaengine_desc_free()``, this can succeed only
+ when DMA_CTRL_REUSE is already set
+
+ - Terminating the channel
+
+- DMA_PREP_CMD
+
+ - If set, the client driver tells DMA controller that passed data in DMA
+ API is command data.
+
+ - Interpretation of command data is DMA controller specific. It can be
+ used for issuing commands to other peripherals/register reads/register
+ writes for which the descriptor should be in different format from
+ normal data descriptors.
+
+General Design Notes
+====================
+
+Most of the DMAEngine drivers you'll see are based on a similar design
+that handles the end of transfer interrupts in the handler, but defer
+most work to a tasklet, including the start of a new transfer whenever
+the previous transfer ended.
+
+This is a rather inefficient design though, because the inter-transfer
+latency will be not only the interrupt latency, but also the
+scheduling latency of the tasklet, which will leave the channel idle
+in between, which will slow down the global transfer rate.
+
+You should avoid this kind of practice, and instead of electing a new
+transfer in your tasklet, move that part to the interrupt handler in
+order to have a shorter idle window (that we can't really avoid
+anyway).
+
+Glossary
+========
+
+- Burst: A number of consecutive read or write operations that
+ can be queued to buffers before being flushed to memory.
+
+- Chunk: A contiguous collection of bursts
+
+- Transfer: A collection of chunks (be it contiguous or not)
--- /dev/null
+==============================
+PXA/MMP - DMA Slave controller
+==============================
+
+Constraints
+===========
+
+a) Transfers hot queuing
+A driver submitting a transfer and issuing it should be granted the transfer
+is queued even on a running DMA channel.
+This implies that the queuing doesn't wait for the previous transfer end,
+and that the descriptor chaining is not only done in the irq/tasklet code
+triggered by the end of the transfer.
+A transfer which is submitted and issued on a phy doesn't wait for a phy to
+stop and restart, but is submitted on a "running channel". The other
+drivers, especially mmp_pdma waited for the phy to stop before relaunching
+a new transfer.
+
+b) All transfers having asked for confirmation should be signaled
+Any issued transfer with DMA_PREP_INTERRUPT should trigger a callback call.
+This implies that even if an irq/tasklet is triggered by end of tx1, but
+at the time of irq/dma tx2 is already finished, tx1->complete() and
+tx2->complete() should be called.
+
+c) Channel running state
+A driver should be able to query if a channel is running or not. For the
+multimedia case, such as video capture, if a transfer is submitted and then
+a check of the DMA channel reports a "stopped channel", the transfer should
+not be issued until the next "start of frame interrupt", hence the need to
+know if a channel is in running or stopped state.
+
+d) Bandwidth guarantee
+The PXA architecture has 4 levels of DMAs priorities : high, normal, low.
+The high priorities get twice as much bandwidth as the normal, which get twice
+as much as the low priorities.
+A driver should be able to request a priority, especially the real-time
+ones such as pxa_camera with (big) throughputs.
+
+Design
+======
+a) Virtual channels
+Same concept as in sa11x0 driver, ie. a driver was assigned a "virtual
+channel" linked to the requestor line, and the physical DMA channel is
+assigned on the fly when the transfer is issued.
+
+b) Transfer anatomy for a scatter-gather transfer
+
+::
+
+ +------------+-----+---------------+----------------+-----------------+
+ | desc-sg[0] | ... | desc-sg[last] | status updater | finisher/linker |
+ +------------+-----+---------------+----------------+-----------------+
+
+This structure is pointed by dma->sg_cpu.
+The descriptors are used as follows :
+
+ - desc-sg[i]: i-th descriptor, transferring the i-th sg
+ element to the video buffer scatter gather
+
+ - status updater
+ Transfers a single u32 to a well known dma coherent memory to leave
+ a trace that this transfer is done. The "well known" is unique per
+ physical channel, meaning that a read of this value will tell which
+ is the last finished transfer at that point in time.
+
+ - finisher: has ddadr=DADDR_STOP, dcmd=ENDIRQEN
+
+ - linker: has ddadr= desc-sg[0] of next transfer, dcmd=0
+
+c) Transfers hot-chaining
+Suppose the running chain is:
+
+::
+
+ Buffer 1 Buffer 2
+ +---------+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+---+
+ | |
+ +----+
+
+After a call to dmaengine_submit(b3), the chain will look like:
+
+::
+
+ Buffer 1 Buffer 2 Buffer 3
+ +---------+----+---+ +----+----+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+-|-+ ^----+----+----+---+
+ | | | |
+ +----+ +----+
+ new_link
+
+If while new_link was created the DMA channel stopped, it is _not_
+restarted. Hot-chaining doesn't break the assumption that
+dma_async_issue_pending() is to be used to ensure the transfer is actually started.
+
+One exception to this rule :
+
+- if Buffer1 and Buffer2 had all their addresses 8 bytes aligned
+
+- and if Buffer3 has at least one address not 4 bytes aligned
+
+- then hot-chaining cannot happen, as the channel must be stopped, the
+ "align bit" must be set, and the channel restarted As a consequence,
+ such a transfer tx_submit() will be queued on the submitted queue, and
+ this specific case if the DMA is already running in aligned mode.
+
+d) Transfers completion updater
+Each time a transfer is completed on a channel, an interrupt might be
+generated or not, up to the client's request. But in each case, the last
+descriptor of a transfer, the "status updater", will write the latest
+transfer being completed into the physical channel's completion mark.
+
+This will speed up residue calculation, for large transfers such as video
+buffers which hold around 6k descriptors or more. This also allows without
+any lock to find out what is the latest completed transfer in a running
+DMA chain.
+
+e) Transfers completion, irq and tasklet
+When a transfer flagged as "DMA_PREP_INTERRUPT" is finished, the dma irq
+is raised. Upon this interrupt, a tasklet is scheduled for the physical
+channel.
+
+The tasklet is responsible for :
+
+- reading the physical channel last updater mark
+
+- calling all the transfer callbacks of finished transfers, based on
+ that mark, and each transfer flags.
+
+If a transfer is completed while this handling is done, a dma irq will
+be raised, and the tasklet will be scheduled once again, having a new
+updater mark.
+
+f) Residue
+Residue granularity will be descriptor based. The issued but not completed
+transfers will be scanned for all of their descriptors against the
+currently running descriptor.
+
+g) Most complicated case of driver's tx queues
+The most tricky situation is when :
+
+ - there are not "acked" transfers (tx0)
+
+ - a driver submitted an aligned tx1, not chained
+
+ - a driver submitted an aligned tx2 => tx2 is cold chained to tx1
+
+ - a driver issued tx1+tx2 => channel is running in aligned mode
+
+ - a driver submitted an aligned tx3 => tx3 is hot-chained
+
+ - a driver submitted an unaligned tx4 => tx4 is put in submitted queue,
+ not chained
+
+ - a driver issued tx4 => tx4 is put in issued queue, not chained
+
+ - a driver submitted an aligned tx5 => tx5 is put in submitted queue, not
+ chained
+
+ - a driver submitted an aligned tx6 => tx6 is put in submitted queue,
+ cold chained to tx5
+
+ This translates into (after tx4 is issued) :
+
+ - issued queue
+
+ ::
+
+ +-----+ +-----+ +-----+ +-----+
+ | tx1 | | tx2 | | tx3 | | tx4 |
+ +---|-+ ^---|-+ ^-----+ +-----+
+ | | | |
+ +---+ +---+
+ - submitted queue
+ +-----+ +-----+
+ | tx5 | | tx6 |
+ +---|-+ ^-----+
+ | |
+ +---+
+
+- completed queue : empty
+
+- allocated queue : tx0
+
+It should be noted that after tx3 is completed, the channel is stopped, and
+restarted in "unaligned mode" to handle tx4.
+
+Author: Robert Jarzmik <robert.jarzmik@free.fr>
pinctl
gpio
misc_devices
+ dmaengine/index
.. only:: subproject and html
This file is handy for status viewing tools in user mode, which can scan
the text format and ignore most of it. More detailed device status
(including class and vendor status) is available from device-specific
-files. For information about the current format of this file, see the
-``Documentation/usb/proc_usb_info.txt`` file in your Linux kernel
-sources.
+files. For information about the current format of this file, see below.
This file, in combination with the poll() system call, can also be used
to detect when devices are added or removed::
1. fbcon=font:<name>
Select the initial font to use. The value 'name' can be any of the
- compiled-in fonts: VGA8x16, 7x14, 10x18, VGA8x8, MINI4x6, RomanLarge,
- SUN8x16, SUN12x22, ProFont6x11, Acorn8x8, PEARL8x8.
+ compiled-in fonts: 10x18, 6x10, 7x14, Acorn8x8, MINI4x6,
+ PEARL8x8, ProFont6x11, SUN12x22, SUN8x16, VGA8x16, VGA8x8.
Note, not all drivers can handle font with widths not divisible by 8,
such as vga16fb.
| tile: | TODO |
| um: | TODO |
| unicore32: | TODO |
- | x86: | ok |
+ | x86: | ok | 64-bit only
| xtensa: | TODO |
-----------------------
Example
-------
-See Documentation/filesystems/dnotify_test.c for an example.
+See tools/testing/selftests/filesystems/dnotify_test.c for an example.
NOTE
----
* ability to pack bitmaps and inode tables into larger virtual groups via the
flex_bg feature
* large file support
-* Inode allocation using large virtual block groups via flex_bg
+* inode allocation using large virtual block groups via flex_bg
* delayed allocation
* large block (up to pagesize) support
-* efficient new ordered mode in JBD2 and ext4(avoid using buffer head to force
+* efficient new ordered mode in JBD2 and ext4 (avoid using buffer head to force
the ordering)
[1] Filesystems with a block size of 1k may see a limit imposed by the
2.2 Candidate features for future inclusion
-* Online defrag (patches available but not well tested)
+* online defrag (patches available but not well tested)
* reduced mke2fs time via lazy itable initialization in conjunction with
the uninit_bg feature (capability to do this is available in e2fsprogs
but a kernel thread to do lazy zeroing of unused inode table blocks
bitmaps and inode table, the userspace tool thus
just passes the new number of blocks.
-EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes
+ EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes
(like i_blocks, i_size, i_flags, ...) from
the specified inode with inode
EXT4_BOOT_LOADER_INO (#5). This is typically
HID events to two separate interfaces:
* the input subsystem, which converts HID events into normal input
device interfaces (such as keyboard, mouse and joystick) and a
-normalised event interface - see Documentation/input/input.txt
+normalised event interface - see Documentation/input/input.rst
* the hiddev interface, which provides fairly raw HID events
The data flow for a HID event produced by a device is something like
2005-03-19 - Dominic Cerquetti <binary1230@yahoo.com>
- added stuff for dance pads, new d-pad->axes mappings
-Later changes may be viewed with 'git log Documentation/input/xpad.txt'
+Later changes may be viewed with
+'git log --follow Documentation/input/devices/xpad.rst'
DO_CPU:
Enable CPU frequency scaling when in laptop mode. (Requires CPUFreq to be setup.
-See Documentation/cpu-freq/user-guide.txt for more info. Disabled by default.)
+See Documentation/admin-guide/pm/cpufreq.rst for more info. Disabled by default.)
CPU_MAXFREQ:
# Should the maximum CPU frequency be adjusted down while on battery?
# Requires CPUFreq to be setup.
-# See Documentation/cpu-freq/user-guide.txt for more info
+# See Documentation/admin-guide/pm/cpufreq.rst for more info
#DO_CPU=0
# When on battery what is the maximum CPU speed that the system should
DIRTY_RATIO=${DIRTY_RATIO:-'40'}
# cpu frequency scaling
-# See Documentation/cpu-freq/user-guide.txt for more info
+# See Documentation/admin-guide/pm/cpufreq.rst for more info
DO_CPU=${CPU_MANAGE:-'0'}
CPU_MAXFREQ=${CPU_MAXFREQ:-'slowest'}
This document tries to describe the design of the rtmutex.c implementation.
It doesn't describe the reasons why rtmutex.c exists. For that please see
-Documentation/rt-mutex.txt. Although this document does explain problems
+Documentation/locking/rt-mutex.txt. Although this document does explain problems
that happen without this code, but that is in the concept to understand
what the code actually is doing.
This class of cards has a bt878a as the PCI interface, and require the bttv driver
for accessing the i2c bus and the gpio pins of the bt8xx chipset.
-Please see Documentation/dvb/cards.txt => o Cards based on the Conexant Bt8xx PCI bridge:
+Please see Documentation/media/dvb-drivers/cards.rst => o Cards based on the Conexant Bt8xx PCI bridge:
Compiling kernel please enable:
Regular case: If the bttv driver detects a bt8xx-based DVB card, all frontend and backend modules will be loaded automatically.
Exceptions are:
- Old TwinHan DST cards or clones with or without CA slot and not containing an Eeprom.
-People running udev please see Documentation/dvb/udev.txt.
+People running udev please see Documentation/media/dvb-drivers/udev.rst.
In the following cases overriding the PCI type detection for dvb-bt8xx might be necessary:
The autodetected values are determined by the cards' "response string".
In your logs see f. ex.: dst_get_device_id: Recognize [DSTMCI].
For bug reports please send in a complete log with verbose=4 activated.
-Please also see Documentation/dvb/ci.txt.
+Please also see Documentation/media/dvb-drivers/ci.rst.
Running multiple cards
~~~~~~~~~~~~~~~~~~~~~~
$ modprobe bttv card=113 card=135
-For a full list of card ID's please see Documentation/video4linux/CARDLIST.bttv.
+For a full list of card ID's please see Documentation/media/v4l-drivers/bttv-cardlist.rst.
In case of further problems please subscribe and send questions to the mailing list: linux-dvb@linuxtv.org.
Probing the cards with broken PCI subsystem ID
*Historical context*: This format specification originates from a
custom, embedded, sliced VBI data format used by the ``ivtv`` driver.
This format has already been informally specified in the kernel sources
-in the file ``Documentation/video4linux/cx2341x/README.vbi`` . The
+in the file ``Documentation/media/v4l-drivers/cx2341x.rst`` . The
maximum size of the payload and other aspects of this format are driven
by the CX23415 MPEG decoder's capabilities and limitations with respect
to extracting, decoding, and displaying sliced VBI data embedded within
* - ``V4L2_MPEG_STREAM_VBI_FMT_IVTV``
- VBI in private packets, IVTV format (documented in the kernel
sources in the file
- ``Documentation/video4linux/cx2341x/README.vbi``)
+ ``Documentation/media/v4l-drivers/cx2341x.rst``)
`http://www.ivtvdriver.org/ <http://www.ivtvdriver.org/>`__
The format is documented in the kernel sources in the file
- ``Documentation/video4linux/cx2341x/README.hm12``
+ ``Documentation/media/v4l-drivers/cx2341x.rst``
* .. _V4L2-PIX-FMT-CPIA1:
- ``V4L2_PIX_FMT_CPIA1``
screen. See Documentation/admin-guide/serial-console.rst for details on setting
up a serial console.
-Read Documentation/admin-guide/oops-tracing.rst to learn how to get any useful
+Read Documentation/admin-guide/bug-hunting.rst to learn how to get any useful
information out of a register+stack dump printed by the kernel on
protection faults (so-called "kernel oops").
-------------------------------
Enable/Disable I2S output of the tuner. This is a private control
that can be accessed only using the subdev interface.
- Refer to Documentation/media/kapi/v4l2-controls for more details.
+ Refer to Documentation/media/kapi/v4l2-controls.rst for more details.
.. flat-table::
:header-rows: 0
[5] "MBIM (Mobile Broadband Interface Model) Registry"
- http://compliance.usb.org/mbim/
-[6] "/dev/bus/usb filesystem output"
- - Documentation/usb/proc_usb_info.txt
+[6] "/sys/kernel/debug/usb/devices output format"
+ - Documentation/driver-api/usb/usb.rst
[7] "/sys/bus/usb/devices/.../descriptors"
- Documentation/ABI/stable/sysfs-bus-usb
(section 'E') for more details.
A driver declares its offload capabilities in netdev->hw_features; see
- Documentation/networking/netdev-features for more. Note that a device
+ Documentation/networking/netdev-features.txt for more. Note that a device
which only advertises NETIF_F_IP[V6]_CSUM must still obey the csum_start
and csum_offset given in the SKB; if it tries to deduce these itself in
hardware (as some NICs do) the driver should check that the values in the
members do not contain a valid value. For TX_RINGs, by default no timestamp
is generated!
-See include/linux/net_tstamp.h and Documentation/networking/timestamping
+See include/linux/net_tstamp.h and Documentation/networking/timestamping.txt
for more information on hardware timestamps.
-------------------------------------------------------------------------------
robust-futex, PI-futex, robust+PI-futex.
More details about priority inheritance can be found in
-Documentation/rt-mutex.txt.
+Documentation/locking/rt-mutex.txt.
If one of the strings listed in /sys/power/state is written to it, the system
will attempt to transition into the corresponding sleep state. Refer to
-Documentation/power/states.txt for a description of each of those states.
+Documentation/admin-guide/pm/sleep-states.rst for a description of each of
+those states.
/sys/power/disk controls the operating mode of hibernation (Suspend-to-Disk).
Specifically, it tells the kernel what to do after creating a hibernation image.
The 'platform' option is only available if the platform provides a special
mechanism to put the system to sleep after creating a hibernation image (ACPI
does that, for example). The 'suspend' option is available if Suspend-to-RAM
-is supported. Refer to Documentation/power/basic_pm_debugging.txt for the
+is supported. Refer to Documentation/power/basic-pm-debugging.txt for the
description of the 'test_resume' option.
To select an option, write the string representing it to /sys/power/disk.
This document only covers the aspects of power management specific to PCI
devices. For general description of the kernel's interfaces related to device
-power management refer to Documentation/power/admin-guide/devices.rst and
+power management refer to Documentation/driver-api/pm/devices.rst and
Documentation/power/runtime_pm.txt.
---------------------------------------------------------------------------
2.4. System-Wide Power Transitions
----------------------------------
There are a few different types of system-wide power transitions, described in
-Documentation/power/admin-guide/devices.rst. Each of them requires devices to be handled
+Documentation/driver-api/pm/devices.rst. Each of them requires devices to be handled
in a specific way and the PM core executes subsystem-level power management
callbacks for this purpose. They are executed in phases such that each phase
involves executing the same subsystem-level callback for every device belonging
pre-hibernation memory contents to be restored before the pre-hibernation system
activity can be resumed.
-As described in Documentation/power/admin-guide/devices.rst, the hibernation image is loaded
+As described in Documentation/driver-api/pm/devices.rst, the hibernation image is loaded
into memory by a fresh instance of the kernel, called the boot kernel, which in
turn is loaded and run by a boot loader in the usual way. After the boot kernel
has loaded the image, it needs to replace its own code and data with the code
At the time of this writing there are two ways to define power management
callbacks for a PCI device driver, the recommended one, based on using a
-dev_pm_ops structure described in Documentation/power/admin-guide/devices.rst, and the
+dev_pm_ops structure described in Documentation/driver-api/pm/devices.rst, and the
"legacy" one, in which the .suspend(), .suspend_late(), .resume_early(), and
.resume() callbacks from struct pci_driver are used. The legacy approach,
however, doesn't allow one to define runtime power management callbacks and is
PCI Bus Power Management Interface Specification, Rev. 1.2
Advanced Configuration and Power Interface (ACPI) Specification, Rev. 3.0b
PCI Express Base Specification, Rev. 2.0
-Documentation/power/admin-guide/devices.rst
+Documentation/driver-api/pm/devices.rst
Documentation/power/runtime_pm.txt
system suspend and resume callbacks for all of those devices, except for the
complete callback, which is then entirely responsible for handling the device
as appropriate. This only applies to system suspend transitions that are not
-related to hibernation (see Documentation/power/admin-guide/devices.rst for more
+related to hibernation (see Documentation/driver-api/pm/devices.rst for more
information).
The PM core does its best to reduce the probability of race conditions between
of people with grand plans and little code (or even prospect of code) to
back them up, and (3) nobody is obligated to review or comment on ideas
posted by others. Beyond that, high-level designs often hide problems
-which are only reviewed when somebody actually tries to implement those
+which are only revealed when somebody actually tries to implement those
designs; for that reason, kernel developers would rather see the code.
If a request-for-comments posting yields little in the way of comments, do
problems. Quite a few "semantic patches" for the kernel have been packaged
under the scripts/coccinelle directory; running "make coccicheck" will run
through those semantic patches and report on any problems found. See
-Documentation/coccinelle.txt for more information.
+Documentation/dev-tools/coccinelle.rst for more information.
Other kinds of portability errors are best found by compiling your code for
other architectures. If you do not happen to have an S/390 system or a
coding-style
email-clients
kernel-enforcement-statement
+ kernel-driver-statement
Other guides to the community that are of interest to most developers are:
--- /dev/null
+Kernel Driver Statement
+-----------------------
+
+Position Statement on Linux Kernel Modules
+==========================================
+
+
+We, the undersigned Linux kernel developers, consider any closed-source
+Linux kernel module or driver to be harmful and undesirable. We have
+repeatedly found them to be detrimental to Linux users, businesses, and
+the greater Linux ecosystem. Such modules negate the openness,
+stability, flexibility, and maintainability of the Linux development
+model and shut their users off from the expertise of the Linux
+community. Vendors that provide closed-source kernel modules force their
+customers to give up key Linux advantages or choose new vendors.
+Therefore, in order to take full advantage of the cost savings and
+shared support benefits open source has to offer, we urge vendors to
+adopt a policy of supporting their customers on Linux with open-source
+kernel code.
+
+We speak only for ourselves, and not for any company we might work for
+today, have in the past, or will in the future.
+
+ - Dave Airlie
+ - Nick Andrew
+ - Jens Axboe
+ - Ralf Baechle
+ - Felipe Balbi
+ - Ohad Ben-Cohen
+ - Muli Ben-Yehuda
+ - Jiri Benc
+ - Arnd Bergmann
+ - Thomas Bogendoerfer
+ - Vitaly Bordug
+ - James Bottomley
+ - Josh Boyer
+ - Neil Brown
+ - Mark Brown
+ - David Brownell
+ - Michael Buesch
+ - Franck Bui-Huu
+ - Adrian Bunk
+ - François Cami
+ - Ralph Campbell
+ - Luiz Fernando N. Capitulino
+ - Mauro Carvalho Chehab
+ - Denis Cheng
+ - Jonathan Corbet
+ - Glauber Costa
+ - Alan Cox
+ - Magnus Damm
+ - Ahmed S. Darwish
+ - Robert P. J. Day
+ - Hans de Goede
+ - Arnaldo Carvalho de Melo
+ - Helge Deller
+ - Jean Delvare
+ - Mathieu Desnoyers
+ - Sven-Thorsten Dietrich
+ - Alexey Dobriyan
+ - Daniel Drake
+ - Alex Dubov
+ - Randy Dunlap
+ - Michael Ellerman
+ - Pekka Enberg
+ - Jan Engelhardt
+ - Mark Fasheh
+ - J. Bruce Fields
+ - Larry Finger
+ - Jeremy Fitzhardinge
+ - Mike Frysinger
+ - Kumar Gala
+ - Robin Getz
+ - Liam Girdwood
+ - Jan-Benedict Glaw
+ - Thomas Gleixner
+ - Brice Goglin
+ - Cyrill Gorcunov
+ - Andy Gospodarek
+ - Thomas Graf
+ - Krzysztof Halasa
+ - Harvey Harrison
+ - Stephen Hemminger
+ - Michael Hennerich
+ - Tejun Heo
+ - Benjamin Herrenschmidt
+ - Kristian Høgsberg
+ - Henrique de Moraes Holschuh
+ - Marcel Holtmann
+ - Mike Isely
+ - Takashi Iwai
+ - Olof Johansson
+ - Dave Jones
+ - Jesper Juhl
+ - Matthias Kaehlcke
+ - Kenji Kaneshige
+ - Jan Kara
+ - Jeremy Kerr
+ - Russell King
+ - Olaf Kirch
+ - Roel Kluin
+ - Hans-Jürgen Koch
+ - Auke Kok
+ - Peter Korsgaard
+ - Jiri Kosina
+ - Mariusz Kozlowski
+ - Greg Kroah-Hartman
+ - Michael Krufky
+ - Aneesh Kumar
+ - Clemens Ladisch
+ - Christoph Lameter
+ - Gunnar Larisch
+ - Anders Larsen
+ - Grant Likely
+ - John W. Linville
+ - Yinghai Lu
+ - Tony Luck
+ - Pavel Machek
+ - Matt Mackall
+ - Paul Mackerras
+ - Roland McGrath
+ - Patrick McHardy
+ - Kyle McMartin
+ - Paul Menage
+ - Thierry Merle
+ - Eric Miao
+ - Akinobu Mita
+ - Ingo Molnar
+ - James Morris
+ - Andrew Morton
+ - Paul Mundt
+ - Oleg Nesterov
+ - Luca Olivetti
+ - S.Çağlar Onur
+ - Pierre Ossman
+ - Keith Owens
+ - Venkatesh Pallipadi
+ - Nick Piggin
+ - Nicolas Pitre
+ - Evgeniy Polyakov
+ - Richard Purdie
+ - Mike Rapoport
+ - Sam Ravnborg
+ - Gerrit Renker
+ - Stefan Richter
+ - David Rientjes
+ - Luis R. Rodriguez
+ - Stefan Roese
+ - Francois Romieu
+ - Rami Rosen
+ - Stephen Rothwell
+ - Maciej W. Rozycki
+ - Mark Salyzyn
+ - Yoshinori Sato
+ - Deepak Saxena
+ - Holger Schurig
+ - Amit Shah
+ - Yoshihiro Shimoda
+ - Sergei Shtylyov
+ - Kay Sievers
+ - Sebastian Siewior
+ - Rik Snel
+ - Jes Sorensen
+ - Alexey Starikovskiy
+ - Alan Stern
+ - Timur Tabi
+ - Hirokazu Takata
+ - Eliezer Tamir
+ - Eugene Teo
+ - Doug Thompson
+ - FUJITA Tomonori
+ - Dmitry Torokhov
+ - Marcelo Tosatti
+ - Steven Toth
+ - Theodore Tso
+ - Matthias Urlichs
+ - Geert Uytterhoeven
+ - Arjan van de Ven
+ - Ivo van Doorn
+ - Rik van Riel
+ - Wim Van Sebroeck
+ - Hans Verkuil
+ - Horst H. von Brand
+ - Dmitri Vorobiev
+ - Anton Vorontsov
+ - Daniel Walker
+ - Johannes Weiner
+ - Harald Welte
+ - Matthew Wilcox
+ - Dan J. Williams
+ - Darrick J. Wong
+ - David Woodhouse
+ - Chris Wright
+ - Bryan Wu
+ - Rafael J. Wysocki
+ - Herbert Xu
+ - Vlad Yasevich
+ - Peter Zijlstra
+ - Bartlomiej Zolnierkiewicz
anything. For the driver testing instructions see
Documentation/power/drivers-testing.txt and for a relatively
complete overview of the power management issues related to
- drivers see Documentation/power/admin-guide/devices.rst .
+ drivers see Documentation/driver-api/pm/devices.rst.
Control:
In general if there is active maintenance of a driver by
The canonical patch message body contains the following:
- - A ``from`` line specifying the patch author (only needed if the person
- sending the patch is not the author).
-
- - An empty line.
+ - A ``from`` line specifying the patch author, followed by an empty
+ line (only needed if the person sending the patch is not the author).
- The body of the explanation, line wrapped at 75 columns, which will
be copied to the permanent changelog to describe this patch.
+ - An empty line.
+
- The ``Signed-off-by:`` lines, described above, which will
also go in the changelog.
Based on https://lkml.org/lkml/2007/10/26/215,
a new LSM is accepted into the kernel when its intent (a description of
what it tries to protect against and in what cases one would expect to
-use it) has been appropriately documented in ``Documentation/security/LSM``.
+use it) has been appropriately documented in ``Documentation/security/LSM.rst``.
This allows an LSM's code to be easily compared to its goals, and so
that end users and distros can make a more informed decision about which
LSMs suit their requirements.
When a process accesses a key, if not already present, it will normally be
cached on one of these keyrings for future accesses to find.
- For more information on using keys, see Documentation/security/keys.txt.
+ For more information on using keys, see ``Documentation/security/keys/*``.
5. LSM
===================
The key request service is part of the key retention service (refer to
-Documentation/security/core.rst). This document explains more fully how
+Documentation/security/keys/core.rst). This document explains more fully how
the requesting algorithm works.
The process starts by either the kernel requesting a service by calling
First of all, you need to enable GAMEPORT support on Linux kernel for
using a joystick with the ALSA driver. For the details of gameport
-support, refer to Documentation/input/joystick.txt.
+support, refer to Documentation/input/joydev/joystick.rst.
The joystick support of ALSA drivers is different between ISA and PCI
cards. In the case of ISA (PnP) cards, it's usually handled by the
What ``model`` option values are available depends on the codec chip.
Check your codec chip from the codec proc file (see "Codec Proc-File"
section below). It will show the vendor/product name of your codec
-chip. Then, see Documentation/sound/HD-Audio-Models.rst file,
+chip. Then, see Documentation/sound/hd-audio/models.rst file,
the section of HD-audio driver. You can find a list of codecs
and ``model`` options belonging to each codec. For example, for Realtek
ALC262 codec chip, pass ``model=ultra`` for devices that are compatible
Mic-boost switch is set as “Mic Boost” or “Mic Boost (6dB)”.
More precise information can be found in
-``Documentation/sound/alsa/ControlNames.txt``.
+``Documentation/sound/designs/control-names.rst``.
Access Flags
------------
dev/ device specific information (eg dev/cdrom/info)
fs/ specific filesystems
filehandle, inode, dentry and quota tuning
- binfmt_misc <Documentation/binfmt_misc.txt>
+ binfmt_misc <Documentation/admin-guide/binfmt-misc.rst>
kernel/ global kernel info / tuning
miscellaneous stuff
net/ networking stuff, for documentation look in:
----------------------------------------------------------
Documentation for the files in /proc/sys/fs/binfmt_misc is
-in Documentation/binfmt_misc.txt.
+in Documentation/admin-guide/binfmt-misc.rst.
3. /proc/sys/fs/mqueue - POSIX message queues filesystem
Further information can be found in the paper of the OLS 2006 talk "hrtimers
and beyond". The paper is part of the OLS 2006 Proceedings Volume 1, which can
be found on the OLS website:
-http://www.linuxsymposium.org/2006/linuxsymposium_procv1.pdf
+https://www.kernel.org/doc/ols/2006/ols2006v1-pages-333-346.pdf
The slides to this talk are available from:
-http://tglx.de/projects/hrtimers/ols2006-hrtimers.pdf
+http://www.cs.columbia.edu/~nahum/w6998/papers/ols2006-hrtimers-slides.pdf
The slides contain five figures (pages 2, 15, 18, 20, 22), which illustrate the
changes in the time(r) related Linux subsystems. Figure #1 (p. 2) shows the
--- /dev/null
+=================================
+Using ftrace to hook to functions
+=================================
+
+.. Copyright 2017 VMware Inc.
+.. Author: Steven Rostedt <srostedt@goodmis.org>
+.. License: The GNU Free Documentation License, Version 1.2
+.. (dual licensed under the GPL v2)
+
+Written for: 4.14
+
+Introduction
+============
+
+The ftrace infrastructure was originially created to attach callbacks to the
+beginning of functions in order to record and trace the flow of the kernel.
+But callbacks to the start of a function can have other use cases. Either
+for live kernel patching, or for security monitoring. This document describes
+how to use ftrace to implement your own function callbacks.
+
+
+The ftrace context
+==================
+
+WARNING: The ability to add a callback to almost any function within the
+kernel comes with risks. A callback can be called from any context
+(normal, softirq, irq, and NMI). Callbacks can also be called just before
+going to idle, during CPU bring up and takedown, or going to user space.
+This requires extra care to what can be done inside a callback. A callback
+can be called outside the protective scope of RCU.
+
+The ftrace infrastructure has some protections agains recursions and RCU
+but one must still be very careful how they use the callbacks.
+
+
+The ftrace_ops structure
+========================
+
+To register a function callback, a ftrace_ops is required. This structure
+is used to tell ftrace what function should be called as the callback
+as well as what protections the callback will perform and not require
+ftrace to handle.
+
+There is only one field that is needed to be set when registering
+an ftrace_ops with ftrace::
+
+.. code-block: c
+
+ struct ftrace_ops ops = {
+ .func = my_callback_func,
+ .flags = MY_FTRACE_FLAGS
+ .private = any_private_data_structure,
+ };
+
+Both .flags and .private are optional. Only .func is required.
+
+To enable tracing call::
+
+.. c:function:: register_ftrace_function(&ops);
+
+To disable tracing call::
+
+.. c:function:: unregister_ftrace_function(&ops);
+
+The above is defined by including the header::
+
+.. c:function:: #include <linux/ftrace.h>
+
+The registered callback will start being called some time after the
+register_ftrace_function() is called and before it returns. The exact time
+that callbacks start being called is dependent upon architecture and scheduling
+of services. The callback itself will have to handle any synchronization if it
+must begin at an exact moment.
+
+The unregister_ftrace_function() will guarantee that the callback is
+no longer being called by functions after the unregister_ftrace_function()
+returns. Note that to perform this guarantee, the unregister_ftrace_function()
+may take some time to finish.
+
+
+The callback function
+=====================
+
+The prototype of the callback function is as follows (as of v4.14)::
+
+.. code-block: c
+
+ void callback_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct pt_regs *regs);
+
+@ip
+ This is the instruction pointer of the function that is being traced.
+ (where the fentry or mcount is within the function)
+
+@parent_ip
+ This is the instruction pointer of the function that called the
+ the function being traced (where the call of the function occurred).
+
+@op
+ This is a pointer to ftrace_ops that was used to register the callback.
+ This can be used to pass data to the callback via the private pointer.
+
+@regs
+ If the FTRACE_OPS_FL_SAVE_REGS or FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED
+ flags are set in the ftrace_ops structure, then this will be pointing
+ to the pt_regs structure like it would be if an breakpoint was placed
+ at the start of the function where ftrace was tracing. Otherwise it
+ either contains garbage, or NULL.
+
+
+The ftrace FLAGS
+================
+
+The ftrace_ops flags are all defined and documented in include/linux/ftrace.h.
+Some of the flags are used for internal infrastructure of ftrace, but the
+ones that users should be aware of are the following:
+
+FTRACE_OPS_FL_SAVE_REGS
+ If the callback requires reading or modifying the pt_regs
+ passed to the callback, then it must set this flag. Registering
+ a ftrace_ops with this flag set on an architecture that does not
+ support passing of pt_regs to the callback will fail.
+
+FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED
+ Similar to SAVE_REGS but the registering of a
+ ftrace_ops on an architecture that does not support passing of regs
+ will not fail with this flag set. But the callback must check if
+ regs is NULL or not to determine if the architecture supports it.
+
+FTRACE_OPS_FL_RECURSION_SAFE
+ By default, a wrapper is added around the callback to
+ make sure that recursion of the function does not occur. That is,
+ if a function that is called as a result of the callback's execution
+ is also traced, ftrace will prevent the callback from being called
+ again. But this wrapper adds some overhead, and if the callback is
+ safe from recursion, it can set this flag to disable the ftrace
+ protection.
+
+ Note, if this flag is set, and recursion does occur, it could cause
+ the system to crash, and possibly reboot via a triple fault.
+
+ It is OK if another callback traces a function that is called by a
+ callback that is marked recursion safe. Recursion safe callbacks
+ must never trace any function that are called by the callback
+ itself or any nested functions that those functions call.
+
+ If this flag is set, it is possible that the callback will also
+ be called with preemption enabled (when CONFIG_PREEMPT is set),
+ but this is not guaranteed.
+
+FTRACE_OPS_FL_IPMODIFY
+ Requires FTRACE_OPS_FL_SAVE_REGS set. If the callback is to "hijack"
+ the traced function (have another function called instead of the
+ traced function), it requires setting this flag. This is what live
+ kernel patches uses. Without this flag the pt_regs->ip can not be
+ modified.
+
+ Note, only one ftrace_ops with FTRACE_OPS_FL_IPMODIFY set may be
+ registered to any given function at a time.
+
+FTRACE_OPS_FL_RCU
+ If this is set, then the callback will only be called by functions
+ where RCU is "watching". This is required if the callback function
+ performs any rcu_read_lock() operation.
+
+ RCU stops watching when the system goes idle, the time when a CPU
+ is taken down and comes back online, and when entering from kernel
+ to user space and back to kernel space. During these transitions,
+ a callback may be executed and RCU synchronization will not protect
+ it.
+
+
+Filtering which functions to trace
+==================================
+
+If a callback is only to be called from specific functions, a filter must be
+set up. The filters are added by name, or ip if it is known.
+
+.. code-block: c
+
+ int ftrace_set_filter(struct ftrace_ops *ops, unsigned char *buf,
+ int len, int reset);
+
+@ops
+ The ops to set the filter with
+
+@buf
+ The string that holds the function filter text.
+@len
+ The length of the string.
+
+@reset
+ Non-zero to reset all filters before applying this filter.
+
+Filters denote which functions should be enabled when tracing is enabled.
+If @buf is NULL and reset is set, all functions will be enabled for tracing.
+
+The @buf can also be a glob expression to enable all functions that
+match a specific pattern.
+
+See Filter Commands in :file:`Documentation/trace/ftrace.txt`.
+
+To just trace the schedule function::
+
+.. code-block: c
+
+ ret = ftrace_set_filter(&ops, "schedule", strlen("schedule"), 0);
+
+To add more functions, call the ftrace_set_filter() more than once with the
+@reset parameter set to zero. To remove the current filter set and replace it
+with new functions defined by @buf, have @reset be non-zero.
+
+To remove all the filtered functions and trace all functions::
+
+.. code-block: c
+
+ ret = ftrace_set_filter(&ops, NULL, 0, 1);
+
+
+Sometimes more than one function has the same name. To trace just a specific
+function in this case, ftrace_set_filter_ip() can be used.
+
+.. code-block: c
+
+ ret = ftrace_set_filter_ip(&ops, ip, 0, 0);
+
+Although the ip must be the address where the call to fentry or mcount is
+located in the function. This function is used by perf and kprobes that
+gets the ip address from the user (usually using debug info from the kernel).
+
+If a glob is used to set the filter, functions can be added to a "notrace"
+list that will prevent those functions from calling the callback.
+The "notrace" list takes precedence over the "filter" list. If the
+two lists are non-empty and contain the same functions, the callback will not
+be called by any function.
+
+An empty "notrace" list means to allow all functions defined by the filter
+to be traced.
+
+.. code-block: c
+
+ int ftrace_set_notrace(struct ftrace_ops *ops, unsigned char *buf,
+ int len, int reset);
+
+This takes the same parameters as ftrace_set_filter() but will add the
+functions it finds to not be traced. This is a separate list from the
+filter list, and this function does not modify the filter list.
+
+A non-zero @reset will clear the "notrace" list before adding functions
+that match @buf to it.
+
+Clearing the "notrace" list is the same as clearing the filter list
+
+.. code-block: c
+
+ ret = ftrace_set_notrace(&ops, NULL, 0, 1);
+
+The filter and notrace lists may be changed at any time. If only a set of
+functions should call the callback, it is best to set the filters before
+registering the callback. But the changes may also happen after the callback
+has been registered.
+
+If a filter is in place, and the @reset is non-zero, and @buf contains a
+matching glob to functions, the switch will happen during the time of
+the ftrace_set_filter() call. At no time will all functions call the callback.
+
+.. code-block: c
+
+ ftrace_set_filter(&ops, "schedule", strlen("schedule"), 1);
+
+ register_ftrace_function(&ops);
+
+ msleep(10);
+
+ ftrace_set_filter(&ops, "try_to_wake_up", strlen("try_to_wake_up"), 1);
+
+is not the same as:
+
+.. code-block: c
+
+ ftrace_set_filter(&ops, "schedule", strlen("schedule"), 1);
+
+ register_ftrace_function(&ops);
+
+ msleep(10);
+
+ ftrace_set_filter(&ops, NULL, 0, 1);
+
+ ftrace_set_filter(&ops, "try_to_wake_up", strlen("try_to_wake_up"), 0);
+
+As the latter will have a short time where all functions will call
+the callback, between the time of the reset, and the time of the
+new setting of the filter.
STH registers an stm class device, through which it provides interface
to userspace and kernelspace software trace sources. See
-Documentation/tracing/stm.txt for more information on that.
+Documentation/trace/stm.txt for more information on that.
MSU can be configured to collect trace data into a system memory
buffer, which can later on be read from its device nodes via read() or
# cat /dev/usb/lp0
More advanced testing can be done with the prn_example
-described in Documentation/usb/gadget-printer.txt.
+described in Documentation/usb/gadget_printer.txt.
20. UAC1 function (virtual ALSA card, using u_audio API)
Watchdog functionality is enabled like any other common watchdog driver. That
is, an application needs to be started that kicks off the watchdog timer. A
- basic application exists in the Documentation/watchdog/src directory called
+ basic application exists in tools/testing/selftests/watchdog/ named
watchdog-test.c. Simply compile the C file and kick it off. If the system
gets into a bad state and hangs, the HPE ProLiant iLO timer register will
not be updated in a timely fashion and a hardware system reset (also known as
If you want to write a program to be compatible with the PC Watchdog
driver, simply use of modify the watchdog test program:
- Documentation/watchdog/src/watchdog-test.c
+ tools/testing/selftests/watchdog/watchdog-test.c
Other IOCTL functions include:
F: drivers/dma/
F: include/linux/dmaengine.h
F: Documentation/devicetree/bindings/dma/
-F: Documentation/dmaengine/
+F: Documentation/driver-api/dmaengine/
T: git git://git.infradead.org/users/vkoul/slave-dma.git
DMA MAPPING HELPERS
# Documentation targets
# ---------------------------------------------------------------------------
-DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs linkcheckdocs
+DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs \
+ linkcheckdocs dochelp refcheckdocs
PHONY += $(DOC_TARGETS)
$(DOC_TARGETS): scripts_basic FORCE
$(Q)$(MAKE) $(build)=Documentation $@
#if BITS_PER_LONG == 64
+/**
+ * do_div - returns 2 values: calculate remainder and update new dividend
+ * @n: pointer to uint64_t dividend (will be updated)
+ * @base: uint32_t divisor
+ *
+ * Summary:
+ * ``uint32_t remainder = *n % base;``
+ * ``*n = *n / base;``
+ *
+ * Return: (uint32_t)remainder
+ *
+ * NOTE: macro parameter @n is evaluated multiple times,
+ * beware of side effects!
+ */
# define do_div(n,base) ({ \
uint32_t __base = (base); \
uint32_t __rem; \
* See lib/bitmap.c for more details.
*/
-/*
+/**
+ * DOC: bitmap overview
+ *
* The available bitmap operations and their rough meaning in the
* case that the bitmap is a single unsigned long are thus:
*
* Note that nbits should be always a compile time evaluable constant.
* Otherwise many inlines will generate horrible code.
*
- * bitmap_zero(dst, nbits) *dst = 0UL
- * bitmap_fill(dst, nbits) *dst = ~0UL
- * bitmap_copy(dst, src, nbits) *dst = *src
- * bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2
- * bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2
- * bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2
- * bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2)
- * bitmap_complement(dst, src, nbits) *dst = ~(*src)
- * bitmap_equal(src1, src2, nbits) Are *src1 and *src2 equal?
- * bitmap_intersects(src1, src2, nbits) Do *src1 and *src2 overlap?
- * bitmap_subset(src1, src2, nbits) Is *src1 a subset of *src2?
- * bitmap_empty(src, nbits) Are all bits zero in *src?
- * bitmap_full(src, nbits) Are all bits set in *src?
- * bitmap_weight(src, nbits) Hamming Weight: number set bits
- * bitmap_set(dst, pos, nbits) Set specified bit area
- * bitmap_clear(dst, pos, nbits) Clear specified bit area
- * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
- * bitmap_find_next_zero_area_off(buf, len, pos, n, mask) as above
- * bitmap_shift_right(dst, src, n, nbits) *dst = *src >> n
- * bitmap_shift_left(dst, src, n, nbits) *dst = *src << n
- * bitmap_remap(dst, src, old, new, nbits) *dst = map(old, new)(src)
- * bitmap_bitremap(oldbit, old, new, nbits) newbit = map(old, new)(oldbit)
- * bitmap_onto(dst, orig, relmap, nbits) *dst = orig relative to relmap
- * bitmap_fold(dst, orig, sz, nbits) dst bits = orig bits mod sz
- * bitmap_parse(buf, buflen, dst, nbits) Parse bitmap dst from kernel buf
- * bitmap_parse_user(ubuf, ulen, dst, nbits) Parse bitmap dst from user buf
- * bitmap_parselist(buf, dst, nbits) Parse bitmap dst from kernel buf
- * bitmap_parselist_user(buf, dst, nbits) Parse bitmap dst from user buf
- * bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region
- * bitmap_release_region(bitmap, pos, order) Free specified bit region
- * bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region
- * bitmap_from_u32array(dst, nbits, buf, nwords) *dst = *buf (nwords 32b words)
- * bitmap_to_u32array(buf, nwords, src, nbits) *buf = *dst (nwords 32b words)
+ * ::
+ *
+ * bitmap_zero(dst, nbits) *dst = 0UL
+ * bitmap_fill(dst, nbits) *dst = ~0UL
+ * bitmap_copy(dst, src, nbits) *dst = *src
+ * bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2
+ * bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2
+ * bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2
+ * bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2)
+ * bitmap_complement(dst, src, nbits) *dst = ~(*src)
+ * bitmap_equal(src1, src2, nbits) Are *src1 and *src2 equal?
+ * bitmap_intersects(src1, src2, nbits) Do *src1 and *src2 overlap?
+ * bitmap_subset(src1, src2, nbits) Is *src1 a subset of *src2?
+ * bitmap_empty(src, nbits) Are all bits zero in *src?
+ * bitmap_full(src, nbits) Are all bits set in *src?
+ * bitmap_weight(src, nbits) Hamming Weight: number set bits
+ * bitmap_set(dst, pos, nbits) Set specified bit area
+ * bitmap_clear(dst, pos, nbits) Clear specified bit area
+ * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
+ * bitmap_find_next_zero_area_off(buf, len, pos, n, mask) as above
+ * bitmap_shift_right(dst, src, n, nbits) *dst = *src >> n
+ * bitmap_shift_left(dst, src, n, nbits) *dst = *src << n
+ * bitmap_remap(dst, src, old, new, nbits) *dst = map(old, new)(src)
+ * bitmap_bitremap(oldbit, old, new, nbits) newbit = map(old, new)(oldbit)
+ * bitmap_onto(dst, orig, relmap, nbits) *dst = orig relative to relmap
+ * bitmap_fold(dst, orig, sz, nbits) dst bits = orig bits mod sz
+ * bitmap_parse(buf, buflen, dst, nbits) Parse bitmap dst from kernel buf
+ * bitmap_parse_user(ubuf, ulen, dst, nbits) Parse bitmap dst from user buf
+ * bitmap_parselist(buf, dst, nbits) Parse bitmap dst from kernel buf
+ * bitmap_parselist_user(buf, dst, nbits) Parse bitmap dst from user buf
+ * bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region
+ * bitmap_release_region(bitmap, pos, order) Free specified bit region
+ * bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region
+ * bitmap_from_u32array(dst, nbits, buf, nwords) *dst = *buf (nwords 32b words)
+ * bitmap_to_u32array(buf, nwords, src, nbits) *buf = *dst (nwords 32b words)
+ *
*/
-/*
- * Also the following operations in asm/bitops.h apply to bitmaps.
+/**
+ * DOC: bitmap bitops
+ *
+ * Also the following operations in asm/bitops.h apply to bitmaps.::
+ *
+ * set_bit(bit, addr) *addr |= bit
+ * clear_bit(bit, addr) *addr &= ~bit
+ * change_bit(bit, addr) *addr ^= bit
+ * test_bit(bit, addr) Is bit set in *addr?
+ * test_and_set_bit(bit, addr) Set bit and return old value
+ * test_and_clear_bit(bit, addr) Clear bit and return old value
+ * test_and_change_bit(bit, addr) Change bit and return old value
+ * find_first_zero_bit(addr, nbits) Position first zero bit in *addr
+ * find_first_bit(addr, nbits) Position first set bit in *addr
+ * find_next_zero_bit(addr, nbits, bit) Position next zero bit in *addr >= bit
+ * find_next_bit(addr, nbits, bit) Position next set bit in *addr >= bit
*
- * set_bit(bit, addr) *addr |= bit
- * clear_bit(bit, addr) *addr &= ~bit
- * change_bit(bit, addr) *addr ^= bit
- * test_bit(bit, addr) Is bit set in *addr?
- * test_and_set_bit(bit, addr) Set bit and return old value
- * test_and_clear_bit(bit, addr) Clear bit and return old value
- * test_and_change_bit(bit, addr) Change bit and return old value
- * find_first_zero_bit(addr, nbits) Position first zero bit in *addr
- * find_first_bit(addr, nbits) Position first set bit in *addr
- * find_next_zero_bit(addr, nbits, bit) Position next zero bit in *addr >= bit
- * find_next_bit(addr, nbits, bit) Position next set bit in *addr >= bit
*/
-/*
+/**
+ * DOC: declare bitmap
* The DECLARE_BITMAP(name,bits) macro, in linux/types.h, can be used
* to declare an array named 'name' of just enough unsigned longs to
* contain all bit positions from 0 to 'bits' - 1.
return __bitmap_parse(buf, buflen, 0, maskp, nmaskbits);
}
-/*
+/**
* BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap.
+ * @n: u64 value
*
* Linux bitmaps are internally arrays of unsigned longs, i.e. 32-bit
* integers in 32-bit environment, and 64-bit integers in 64-bit one.
((unsigned long) ((u64)(n) >> 32))
#endif
-/*
+/**
* bitmap_from_u64 - Check and swap words within u64.
* @mask: source bitmap
* @dst: destination bitmap
*
- * In 32-bit Big Endian kernel, when using (u32 *)(&val)[*]
+ * In 32-bit Big Endian kernel, when using ``(u32 *)(&val)[*]``
* to read u64 mask, we will get the wrong word.
- * That is "(u32 *)(&val)[0]" gets the upper 32 bits,
+ * That is ``(u32 *)(&val)[0]`` gets the upper 32 bits,
* but we expect the lower 32-bits of u64.
*/
static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
}
#endif
-/*
- * Determine whether some value is a power of two, where zero is
+/**
+ * is_power_of_2() - check if a value is a power of two
+ * @n: the value to check
+ *
+ * Determine whether some value is a power of two, where zero is
* *not* considered a power of two.
+ * Return: true if @n is a power of 2, otherwise false.
*/
-
static inline __attribute__((const))
bool is_power_of_2(unsigned long n)
{
return (n != 0 && ((n & (n - 1)) == 0));
}
-/*
- * round up to nearest power of two
+/**
+ * __roundup_pow_of_two() - round up to nearest power of two
+ * @n: value to round up
*/
static inline __attribute__((const))
unsigned long __roundup_pow_of_two(unsigned long n)
return 1UL << fls_long(n - 1);
}
-/*
- * round down to nearest power of two
+/**
+ * __rounddown_pow_of_two() - round down to nearest power of two
+ * @n: value to round down
*/
static inline __attribute__((const))
unsigned long __rounddown_pow_of_two(unsigned long n)
}
/**
- * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
- * @n - parameter
+ * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value
+ * @n: parameter
*
* constant-capable log of base 2 calculation
* - this can be used to initialise global variables from constant data, hence
- * the massive ternary operator construction
+ * the massive ternary operator construction
*
* selects the appropriately-sized optimised version depending on sizeof(n)
*/
/**
* roundup_pow_of_two - round the given value up to nearest power of two
- * @n - parameter
+ * @n: parameter
*
* round the given value up to the nearest power of two
* - the result is undefined when n == 0
/**
* rounddown_pow_of_two - round the given value down to nearest power of two
- * @n - parameter
+ * @n: parameter
*
* round the given value down to the nearest power of two
* - the result is undefined when n == 0
__rounddown_pow_of_two(n) \
)
+static inline __attribute_const__
+int __order_base_2(unsigned long n)
+{
+ return n > 1 ? ilog2(n - 1) + 1 : 0;
+}
+
/**
* order_base_2 - calculate the (rounded up) base 2 order of the argument
* @n: parameter
* ob2(5) = 3
* ... and so on.
*/
-
-static inline __attribute_const__
-int __order_base_2(unsigned long n)
-{
- return n > 1 ? ilog2(n - 1) + 1 : 0;
-}
-
#define order_base_2(n) \
( \
__builtin_constant_p(n) ? ( \
/**
* div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 32bit divisor
+ * @remainder: pointer to unsigned 32bit remainder
+ *
+ * Return: sets ``*remainder``, then returns dividend / divisor
*
* This is commonly provided by 32bit archs to provide an optimized 64bit
* divide.
/**
* div_s64_rem - signed 64bit divide with 32bit divisor with remainder
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 32bit divisor
+ * @remainder: pointer to signed 32bit remainder
+ *
+ * Return: sets ``*remainder``, then returns dividend / divisor
*/
static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
/**
* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 64bit divisor
+ * @remainder: pointer to unsigned 64bit remainder
+ *
+ * Return: sets ``*remainder``, then returns dividend / divisor
*/
static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
/**
* div64_u64 - unsigned 64bit divide with 64bit divisor
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 64bit divisor
+ *
+ * Return: dividend / divisor
*/
static inline u64 div64_u64(u64 dividend, u64 divisor)
{
/**
* div64_s64 - signed 64bit divide with 64bit divisor
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 64bit divisor
+ *
+ * Return: dividend / divisor
*/
static inline s64 div64_s64(s64 dividend, s64 divisor)
{
/**
* div_u64 - unsigned 64bit divide with 32bit divisor
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 32bit divisor
*
* This is the most common 64bit divide and should be used if possible,
* as many 32bit archs can optimize this variant better than a full 64bit
/**
* div_s64 - signed 64bit divide with 32bit divisor
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 32bit divisor
*/
#ifndef div_s64
static inline s64 div_s64(s64 dividend, s32 divisor)
#include <asm/page.h>
-/*
+/**
+ * DOC: bitmap introduction
+ *
* bitmaps provide an array of bits, implemented using an an
* array of unsigned longs. The number of valid bits in a
* given bitmap does _not_ need to be an exact multiple of
}
/**
- * crc32_generic_shift - Append len 0 bytes to crc, in logarithmic time
+ * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time
* @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient)
* @len: The number of bytes. @crc is multiplied by x^(8*@len)
* @polynomial: The modulus used to reduce the result to 32 bits.
/**
* crc4 - calculate the 4-bit crc of a value.
- * @crc: starting crc4
+ * @c: starting crc4
* @x: value to checksum
* @bits: number of bits in @x to checksum
*
#include <linux/crc8.h>
#include <linux/printk.h>
-/*
+/**
* crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
*
- * table: table to be filled.
- * polynomial: polynomial for which table is to be filled.
+ * @table: table to be filled.
+ * @polynomial: polynomial for which table is to be filled.
*/
void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
{
}
EXPORT_SYMBOL(crc8_populate_msb);
-/*
+/**
* crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
*
- * table: table to be filled.
- * polynomial: polynomial for which table is to be filled.
+ * @table: table to be filled.
+ * @polynomial: polynomial for which table is to be filled.
*/
void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
{
}
EXPORT_SYMBOL(crc8_populate_lsb);
-/*
+/**
* crc8 - calculate a crc8 over the given input data.
*
- * table: crc table used for calculation.
- * pdata: pointer to data buffer.
- * nbytes: number of bytes in data buffer.
- * crc: previous returned crc8 value.
+ * @table: crc table used for calculation.
+ * @pdata: pointer to data buffer.
+ * @nbytes: number of bytes in data buffer.
+ * @crc: previous returned crc8 value.
*/
u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc)
{
EXPORT_SYMBOL(__div64_32);
#endif
+/**
+ * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
+ * @dividend: 64bit dividend
+ * @divisor: 64bit divisor
+ * @remainder: 64bit remainder
+ */
#ifndef div_s64_rem
s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) && !defined(CPU_NO_EFFICIENT_FFS)
/* If __ffs is available, the even/odd algorithm benchmarks slower. */
+
+/**
+ * gcd - calculate and return the greatest common divisor of 2 unsigned longs
+ * @a: first value
+ * @b: second value
+ */
unsigned long gcd(unsigned long a, unsigned long b)
{
unsigned long r = a | b;
#endif
static u32 cn_test_timer_counter;
-static void cn_test_timer_func(unsigned long __data)
+static void cn_test_timer_func(struct timer_list *unused)
{
struct cn_msg *m;
char data[32];
- pr_debug("%s: timer fired with data %lu\n", __func__, __data);
+ pr_debug("%s: timer fired\n", __func__);
m = kzalloc(sizeof(*m) + sizeof(data), GFP_ATOMIC);
if (m) {
goto err_out;
}
- setup_timer(&cn_test_timer, cn_test_timer_func, 0);
+ timer_setup(&cn_test_timer, cn_test_timer_func, 0);
mod_timer(&cn_test_timer, jiffies + msecs_to_jiffies(1000));
pr_info("initialized with id={%u.%u}\n",
--- /dev/null
+#!/bin/sh
+# Treewide grep for references to files under Documentation, and report
+# non-existing files in stderr.
+
+for f in $(git ls-files); do
+ for ref in $(grep -ho "Documentation/[A-Za-z0-9_.,~/*+-]*" "$f"); do
+ # presume trailing . and , are not part of the name
+ ref=${ref%%[.,]}
+
+ # use ls to handle wildcards
+ if ! ls $ref >/dev/null 2>&1; then
+ echo "$f: $ref" >&2
+ fi
+ done
+done
--- /dev/null
+#!/bin/bash
+# (c) 2017, Jonathan Corbet <corbet@lwn.net>
+# sayli karnik <karniksayli1995@gmail.com>
+#
+# This script detects files with kernel-doc comments for exported functions
+# that are not included in documentation.
+#
+# usage: Run 'scripts/find-unused-docs.sh directory' from top level of kernel
+# tree.
+#
+# example: $scripts/find-unused-docs.sh drivers/scsi
+#
+# Licensed under the terms of the GNU GPL License
+
+if ! [ -d "Documentation" ]; then
+ echo "Run from top level of kernel tree"
+ exit 1
+fi
+
+if [ "$#" -ne 1 ]; then
+ echo "Usage: scripts/find-unused-docs.sh directory"
+ exit 1
+fi
+
+if ! [ -d "$1" ]; then
+ echo "Directory $1 doesn't exist"
+ exit 1
+fi
+
+cd "$( dirname "${BASH_SOURCE[0]}" )"
+cd ..
+
+cd Documentation/
+
+echo "The following files contain kerneldoc comments for exported functions \
+that are not used in the formatted documentation"
+
+# FILES INCLUDED
+
+files_included=($(grep -rHR ".. kernel-doc" --include \*.rst | cut -d " " -f 3))
+
+declare -A FILES_INCLUDED
+
+for each in "${files_included[@]}"; do
+ FILES_INCLUDED[$each]="$each"
+ done
+
+cd ..
+
+# FILES NOT INCLUDED
+
+for file in `find $1 -name '*.c'`; do
+
+ if [[ ${FILES_INCLUDED[$file]+_} ]]; then
+ continue;
+ fi
+ str=$(scripts/kernel-doc -text -export "$file" 2>/dev/null)
+ if [[ -n "$str" ]]; then
+ echo "$file"
+ fi
+ done
+
my $nested;
if ($x =~ /(struct|union)\s+(\w+)\s*{(.*)}/) {
- #my $decl_type = $1;
+ my $decl_type = $1;
$declaration_name = $2;
my $members = $3;
$members =~ s/DECLARE_HASHTABLE\s*\(([^,)]+), ([^,)]+)\)/unsigned long $1\[1 << (($2) - 1)\]/gos;
create_parameterlist($members, ';', $file);
- check_sections($file, $declaration_name, "struct", $sectcheck, $struct_actual, $nested);
+ check_sections($file, $declaration_name, $decl_type, $sectcheck, $struct_actual, $nested);
output_declaration($declaration_name,
'struct',
if ($x =~ /enum\s+(\w+)\s*{(.*)}/) {
$declaration_name = $1;
my $members = $2;
+ my %_members;
+
$members =~ s/\s+$//;
foreach my $arg (split ',', $members) {
print STDERR "${file}:$.: warning: Enum value '$arg' ".
"not described in enum '$declaration_name'\n";
}
-
+ $_members{$arg} = 1;
}
+ while (my ($k, $v) = each %parameterdescs) {
+ if (!exists($_members{$k})) {
+ print STDERR "${file}:$.: warning: Excess enum value " .
+ "'$k' description in '$declaration_name'\n";
+ }
+ }
+
output_declaration($declaration_name,
'enum',
{'enum' => $declaration_name,
} else {
if ($nested !~ m/\Q$sects[$sx]\E/) {
print STDERR "${file}:$.: warning: " .
- "Excess struct/union/enum/typedef member " .
+ "Excess $decl_type member " .
"'$sects[$sx]' " .
"description in '$decl_name'\n";
++$warnings;
git.samba.org / sfrench / cifs-2.6.git / commitdiff