[PATCH v2 1/2] of/fdt: export fdt blob as /sys/firmware/fdt

On Tue, Nov 11, 2014 at 4:25 PM, Rob Herring [off-list ref] wrote:

On Tue, Nov 11, 2014 at 8:42 AM, Grant Likely [off-list ref] wrote:

quoted

On Mon, 10 Nov 2014 19:47:01 +0100
, Ard Biesheuvel [off-list ref]
 wrote:

quoted

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 blob needs to
be preserved as early as possible by calling preserve_fdt().

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 <redacted>

On further thought, nak. I want tree modifications to be treated as
bugs. Do a checksum CRC32 or check. It's simpler and it can be extended
to us an in-blob CRC when the file format gets upreved to include one.

Why? MIPS Octeon is full of them BTW. So the rule is any modifications
or fixups have to be on the unflattened tree?

That, or we require the fixups to explicitly clean up the CRC after
themselves. That will force them to be visible. Anything using the
fdt_*() write functions could potentially take care of it
automatically. That would make it immediately discoverable where
changes are being made in the tree.

g.