1 What: /sys/firmware/devicetree/* 1 What: /sys/firmware/devicetree/*
2 Date: November 2013 2 Date: November 2013
3 Contact: Grant Likely <grant.likely@arm. !! 3 Contact: Grant Likely <grant.likely@linaro.org>
4 Description: 4 Description:
5 When using OpenFirmware or a F 5 When using OpenFirmware or a Flattened Device Tree to enumerate
6 hardware, the device tree stru 6 hardware, the device tree structure will be exposed in this
7 directory. 7 directory.
8 8
9 It is possible for multiple de 9 It is possible for multiple device-tree directories to exist.
10 Some device drivers use a sepa 10 Some device drivers use a separate detached device tree which
11 have no attachment to the syst 11 have no attachment to the system tree and will appear in a
12 different subdirectory under / 12 different subdirectory under /sys/firmware/devicetree.
13 13
14 Userspace must not use the /sy 14 Userspace must not use the /sys/firmware/devicetree/base
15 path directly, but instead sho 15 path directly, but instead should follow /proc/device-tree
16 symlink. It is possible that t 16 symlink. It is possible that the absolute path will change
17 in the future, but the symlink 17 in the future, but the symlink is the stable ABI.
18 18
19 The /proc/device-tree symlink 19 The /proc/device-tree symlink replaces the devicetree /proc
20 filesystem support, and has la 20 filesystem support, and has largely the same semantics and
21 should be compatible with exis 21 should be compatible with existing userspace.
22 22
23 The contents of /sys/firmware/ 23 The contents of /sys/firmware/devicetree/ is a
24 hierarchy of directories, one 24 hierarchy of directories, one per device tree node. The
25 directory name is the resolved 25 directory name is the resolved path component name (node
26 name plus address). Properties 26 name plus address). Properties are represented as files
27 in the directory. The contents 27 in the directory. The contents of each file is the exact
28 binary data from the device tr 28 binary data from the device tree.
29 <<
30 What: /sys/firmware/fdt <<
31 Date: February 2015 <<
32 KernelVersion: 3.19 <<
33 Contact: Frank Rowand <frowand.list@gmai <<
34 Description: <<
35 Exports the FDT blob that was <<
36 the bootloader. This allows us <<
37 as kexec to access the raw bin <<
38 useful when debugging since it <<
39 made to the blob by the bootlo <<
40 <<
41 The fact that this node does n <<
42 /sys/firmware/device-tree is d <<
43 on arm64 UEFI/ACPI systems to <<
44 and ACPI entry points, but the <<
45 and used to configure the syst <<
46 <<
47 A CRC32 checksum is calculated <<
48 blob, and verified at late_ini <<
49 entry is instantiated only if <<
50 i.e., if the FDT blob has not <<
51 time. Otherwise, a warning is <<
52 Users: kexec, debugging <<
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