[coreboot] GRUB2 Questions

Patrick Georgi patrick at georgi-clan.de
Fri May 9 21:01:09 CEST 2008

Am Fri, 09 May 2008 16:00:42 +0200
schrieb Stefan Reinauer <stepan at coresystems.de>:
> Peter Stuge wrote:
> > Is (memdisk) the LAR? Could we harmonize the names in that case?
> I think grub2 splits this up.. There is a larfs, and a memdisk device.
> It used to be (lar) iirc but Patrick adapted it to existing grub2
> behavior. Not sure if I get this right. memdisk might also only be
> the grub2 compiled in "memdisk", while (lar) at least used to be the
> hunk that was found in the rom.
(lar) existed only in the gsoc tree. After the grub2 team reimplemented
the linuxbios support, I adopted their tree and continued work from
there. As they have their own ramdisk mechanism now, I adopted it (6
lines patch vs. several new files).

The situation on the i386-linuxbios platform is now as follows:

(memdisk) points to the ROM area by default (currently hardcoded to
4gb - 256kb or so, eventually this should be read out from the ROM), so
together with lar (which implements lar as filesystem), you get instant
access to the archive structure of a coreboot v3 firmware.

If you're on coreboot v2, or if you use coreboot v3 and don't want to
add files to the archive for some reason, you can use a diskimage
module, as created by grub-mkdiskimage, to redirect (memdisk) to a
different memory location - one inside the diskimage module, which
carries the data you passed to grub-mkdiskimage.

So (memdisk) is supposed to Do The Right Thing on v3, and provide a
sensible way to have a ramdisk with v2.
As it's an abstraction, neither (firmware), nor (lar) (it could be cpio
formatted, as well) fits well.

And given that the other platforms use (memdisk), reusing that name
can't hurt.


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