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| author | Grant Likely <grant.likely@linaro.org> | 2014-02-20 22:02:11 +0400 |
|---|---|---|
| committer | Grant Likely <grant.likely@linaro.org> | 2014-03-12 00:48:26 +0400 |
| commit | 75b57ecf9d1d1e17d099ab13b8f48e6e038676be (patch) | |
| tree | 1fcf03dae1722cf5c7917023a404958be2bce036 /Documentation/ABI/testing/sysfs-firmware-ofw | |
| parent | dab2310d9d90eded48625c5382c6a60389bf8ca9 (diff) | |
| download | linux-75b57ecf9d1d1e17d099ab13b8f48e6e038676be.tar.xz | |
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>
Diffstat (limited to 'Documentation/ABI/testing/sysfs-firmware-ofw')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-firmware-ofw | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-firmware-ofw b/Documentation/ABI/testing/sysfs-firmware-ofw new file mode 100644 index 000000000000..f562b188e71d --- /dev/null +++ b/Documentation/ABI/testing/sysfs-firmware-ofw @@ -0,0 +1,28 @@ +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. |