[PATCH] of/fdt: export fdt blob as /sys/firmware/fdt

[Ard Biesheuvel]

On 10 November 2014 17:57, Arnd Bergmann <arnd at arndb.de> wrote:
> On Monday 10 November 2014 17:51:45 Ard Biesheuvel wrote:
>> Create a new /sys entry '/sys/firmware/fdt' to export the FDT blob
>> that was passed to the kernel by the bootloader. This allows userland
>> applications such as kexec to access the raw binary.
>>
>> 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.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>
> Can you elaborate on the motivation? Initially the fdt format was
> introduced to make it easy to pass the information from /proc/device-tree
> to the next kernel for kexec. Are you interested in cases where this does
> not work?
>

/sys/firmware/device-tree only gets populated if you are really
booting in DT mode, i.e., when the device tree is unflattened.
However, in ACPI mode we still need to access the data that was
communicated between UEFI and the kernel in the /chosen node if we
want to support kexec under UEFI.

-- 
Ard.