| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152 |
- What: /sys/firmware/devicetree/*
- Date: November 2013
- Contact: Grant Likely <[email protected]>, [email protected]
- 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 <[email protected]>, [email protected]
- 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
|
