On Mon, Sep 30, 2013 at 07:27:58PM +0100, Grant Likely wrote:

...

So ... I guess that would modify the stub behaviour to:

• Look for an FDT_GUID configuration table.
• If there, use it.
• If not there, require one to be loaded based on command line.

Create a mostly empty one for passing freeform data to the kernel proper; this is what it will look like on ACPI systems.

OK. So we push the actual error condition of missing tree down to stub? Makes sense.

...

The x86 code uses bootparam to pass the kernel command line. Could we use the FDT exists) for the kernel command line too? This would make more code shared between x86 and ARM*, since otherwise we would need to explicitly implement (UCS?) command line passing to stub?

Yes, I think that makes sense. That also means GRUB will need to always create an FDT, even if it is empty.

Yes. This would be my preference.

The other option would be to pass the command line via the LoadOptions from the EFI_LOADED_IMAGE protocol. I believe that is what Roy's patches currently rely on for getting a command line.

Since the current code doesn't UEFI-wise "load" the stub image, we'd effectively need to reverse-reconstruct GRUB's runtime environment, which I really wouldn't like.

/ Leif