mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
52 lines
2.2 KiB
52 lines
2.2 KiB
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
|
|
|