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1What: /sys/firmware/devicetree/*2Date: November 20133Contact: Grant Likely <grant.likely@arm.com>, devicetree@vger.kernel.org4Description:5 When using OpenFirmware or a Flattened Device Tree to enumerate6 hardware, the device tree structure will be exposed in this7 directory.8 9 It is possible for multiple device-tree directories to exist.10 Some device drivers use a separate detached device tree which11 have no attachment to the system tree and will appear in a12 different subdirectory under /sys/firmware/devicetree.13 14 Userspace must not use the /sys/firmware/devicetree/base15 path directly, but instead should follow /proc/device-tree16 symlink. It is possible that the absolute path will change17 in the future, but the symlink is the stable ABI.18 19 The /proc/device-tree symlink replaces the devicetree /proc20 filesystem support, and has largely the same semantics and21 should be compatible with existing userspace.22 23 The contents of /sys/firmware/devicetree/ is a24 hierarchy of directories, one per device tree node. The25 directory name is the resolved path component name (node26 name plus address). Properties are represented as files27 in the directory. The contents of each file is the exact28 binary data from the device tree.29 30What: /sys/firmware/fdt31Date: February 201532KernelVersion: 3.1933Contact: Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org34Description:35 Exports the FDT blob that was passed to the kernel by36 the bootloader. This allows userland applications such37 as kexec to access the raw binary. This blob is also38 useful when debugging since it contains any changes39 made to the blob by the bootloader.40 41 The fact that this node does not reside under42 /sys/firmware/device-tree is deliberate: FDT is also used43 on arm64 UEFI/ACPI systems to communicate just the UEFI44 and ACPI entry points, but the FDT is never unflattened45 and used to configure the system.46 47 A CRC32 checksum is calculated over the entire FDT48 blob, and verified at late_initcall time. The sysfs49 entry is instantiated only if the checksum is valid,50 i.e., if the FDT blob has not been modified in the mean51 time. Otherwise, a warning is printed.52Users: kexec, debugging53