linux_dsm_epyc7002/Documentation/ABI/testing/sysfs-firmware-ofw
Grant Likely 75b57ecf9d of: Make device nodes kobjects so they show up in sysfs
Device tree nodes are already treated as objects, and we already want to
expose them to userspace which is done using the /proc filesystem today.
Right now the kernel has to do a lot of work to keep the /proc view in
sync with the in-kernel representation. If device_nodes are switched to
be kobjects then the device tree code can be a whole lot simpler. It
also turns out that switching to using /sysfs from /proc results in
smaller code and data size, and the userspace ABI won't change if
/proc/device-tree symlinks to /sys/firmware/devicetree/base.

v7: Add missing sysfs_bin_attr_init()
v6: Add __of_add_property() early init fixes from Pantelis
v5: Rename firmware/ofw to firmware/devicetree
    Fix updating property values in sysfs
v4: Fixed build error on Powerpc
    Fixed handling of dynamic nodes on powerpc
v3: Fixed handling of duplicate attribute and child node names
v2: switch to using sysfs bin_attributes which solve the problem of
    reporting incorrect property size.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
2014-03-11 20:48:26 +00:00

29 lines
1.2 KiB
Plaintext

What: /sys/firmware/devicetree/*
Date: November 2013
Contact: Grant Likely <grant.likely@linaro.org>
Description:
When using OpenFirmware or a Flattened Device Tree to enumerate
hardware, the device tree structure will be exposed in this
directory.
It is possible for multiple device-tree directories to exist.
Some device drivers use a separate detached device tree which
have no attachment to the system tree and will appear in a
different subdirectory under /sys/firmware/devicetree.
Userspace must not use the /sys/firmware/devicetree/base
path directly, but instead should follow /proc/device-tree
symlink. It is possible that the absolute path will change
in the future, but the symlink is the stable ABI.
The /proc/device-tree symlink replaces the devicetree /proc
filesystem support, and has largely the same semantics and
should be compatible with existing userspace.
The contents of /sys/firmware/devicetree/ is a
hierarchy of directories, one per device tree node. The
directory name is the resolved path component name (node
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.