Based on kernel version 4.13.3. Page generated on 2017-09-23 13:54 EST.
1 What: /sys/firmware/devicetree/* 2 Date: November 2013 3 Contact: Grant Likely <email@example.com>, firstname.lastname@example.org 4 Description: 5 When using OpenFirmware or a Flattened Device Tree to enumerate 6 hardware, the device tree structure will be exposed in this 7 directory. 8 9 It is possible for multiple device-tree directories to exist. 10 Some device drivers use a separate detached device tree which 11 have no attachment to the system tree and will appear in a 12 different subdirectory under /sys/firmware/devicetree. 13 14 Userspace must not use the /sys/firmware/devicetree/base 15 path directly, but instead should follow /proc/device-tree 16 symlink. It is possible that the absolute path will change 17 in the future, but the symlink is the stable ABI. 18 19 The /proc/device-tree symlink replaces the devicetree /proc 20 filesystem support, and has largely the same semantics and 21 should be compatible with existing userspace. 22 23 The contents of /sys/firmware/devicetree/ is a 24 hierarchy of directories, one per device tree node. The 25 directory name is the resolved path component name (node 26 name plus address). Properties are represented as files 27 in the directory. The contents of each file is the exact 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 <email@example.com>, firstname.lastname@example.org 34 Description: 35 Exports the FDT blob that was passed to the kernel by 36 the bootloader. This allows userland applications such 37 as kexec to access the raw binary. This blob is also 38 useful when debugging since it contains any changes 39 made to the blob by the bootloader. 40 41 The fact that this node does not reside under 42 /sys/firmware/device-tree is deliberate: FDT is also used 43 on arm64 UEFI/ACPI systems to communicate just the UEFI 44 and ACPI entry points, but the FDT is never unflattened 45 and used to configure the system. 46 47 A CRC32 checksum is calculated over the entire FDT 48 blob, and verified at late_initcall time. The sysfs 49 entry is instantiated only if the checksum is valid, 50 i.e., if the FDT blob has not been modified in the mean 51 time. Otherwise, a warning is printed. 52 Users: kexec, debugging