Merge tag 'fbdev-v4.13' of git://github.com/bzolnier/linux

[sfrench/cifs-2.6.git] / Documentation / ABI / testing / sysfs-firmware-ofw

diff --git a/Documentation/ABI/testing/sysfs-firmware-ofw b/Documentation/ABI/testing/sysfs-firmware-ofw
index f562b188e71d0afda7c080c52649fad1fb0f0b7b..edcab3ccfcc0ed362a78b31e53115d63dbdc412f 100644 (file)
--- a/Documentation/ABI/testing/sysfs-firmware-ofw
+++ b/Documentation/ABI/testing/sysfs-firmware-ofw
@@ -1,6 +1,6 @@
 What:          /sys/firmware/devicetree/*
 Date:          November 2013
-Contact:       Grant Likely <grant.likely@linaro.org>
+Contact:       Grant Likely <grant.likely@arm.com>, devicetree@vger.kernel.org
 Description:
                When using OpenFirmware or a Flattened Device Tree to enumerate
                hardware, the device tree structure will be exposed in this
@@ -26,3 +26,27 @@ Description:
                name plus address). Properties are represented as files
                in the directory. The contents of each file is the exact
                binary data from the device tree.
+
+What:          /sys/firmware/fdt
+Date:          February 2015
+KernelVersion: 3.19
+Contact:       Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org
+Description:
+               Exports the FDT blob that was passed to the kernel by
+               the bootloader. This allows userland applications such
+               as kexec to access the raw binary. This blob is also
+               useful when debugging since it contains any changes
+               made to the blob by the bootloader.
+
+               The fact that this node does not reside under
+               /sys/firmware/device-tree is deliberate: FDT is also used
+               on arm64 UEFI/ACPI systems to communicate just the UEFI
+               and ACPI entry points, but the FDT is never unflattened
+               and used to configure the system.
+
+               A CRC32 checksum is calculated over the entire FDT
+               blob, and verified at late_initcall time. The sysfs
+               entry is instantiated only if the checksum is valid,
+               i.e., if the FDT blob has not been modified in the mean
+               time. Otherwise, a warning is printed.
+Users:         kexec, debugging