Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

[sfrench/cifs-2.6.git] / Documentation / driver-api / s390-drivers.rst

diff --git a/Documentation/driver-api/s390-drivers.rst b/Documentation/driver-api/s390-drivers.rst
index ecf8851d35651161542f65a62c5c1d7ed631ffd8..30e6aa7e160b7b28b6cf4b5252e50df62bac9f98 100644 (file)
--- a/Documentation/driver-api/s390-drivers.rst
+++ b/Documentation/driver-api/s390-drivers.rst
@@ -22,9 +22,28 @@ While most I/O devices on a s390 system are typically driven through the
 channel I/O mechanism described here, there are various other methods
 (like the diag interface). These are out of the scope of this document.
 
+The s390 common I/O layer also provides access to some devices that are
+not strictly considered I/O devices. They are considered here as well,
+although they are not the focus of this document.
+
 Some additional information can also be found in the kernel source under
 Documentation/s390/driver-model.txt.
 
+The css bus
+===========
+
+The css bus contains the subchannels available on the system. They fall
+into several categories:
+
+* Standard I/O subchannels, for use by the system. They have a child
+  device on the ccw bus and are described below.
+* I/O subchannels bound to the vfio-ccw driver. See
+  Documentation/s390/vfio-ccw.txt.
+* Message subchannels. No Linux driver currently exists.
+* CHSC subchannels (at most one). The chsc subchannel driver can be used
+  to send asynchronous chsc commands.
+* eADM subchannels. Used for talking to storage class memory.
+
 The ccw bus
 ===========
 
@@ -102,10 +121,15 @@ ccw group devices
 Generic interfaces
 ==================
 
-Some interfaces are available to other drivers that do not necessarily
-have anything to do with the busses described above, but still are
-indirectly using basic infrastructure in the common I/O layer. One
-example is the support for adapter interrupts.
+The following section contains interfaces in use not only by drivers
+dealing with ccw devices, but drivers for various other s390 hardware
+as well.
+
+Adapter interrupts
+------------------
+
+The common I/O layer provides helper functions for dealing with adapter
+interrupts and interrupt vectors.
 
 .. kernel-doc:: drivers/s390/cio/airq.c
    :export: