What: /sys/firmware/devicetree/* Date: November 2013 Contact: Grant Likely <grant.likely@arm.com>, devicetree@vger.kernel.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. What: /sys/firmware/fdt Date: February 2015 KernelVersion: 3.19 Contact: Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org Description: Exports the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary. This blob is also useful when debugging since it contains any changes made to the blob by the bootloader. The fact that this node does not reside under /sys/firmware/device-tree is deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system. A CRC32 checksum is calculated over the entire FDT blob, and verified at late_initcall time. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed. Users: kexec, debugging