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