Steve's blog

All of my improvements have been committed into the various Debian packages involved, and the latest release candidate for Jessie's debian-installer build (RC2) works just as well as my test builds on the Bay Trail system I've been using (Asus X205TA). Job done! :-)

I'm still hoping to maybe get more hardware support for this particular hardware included in Jessie, but I can't promise. The mixed EFI work has also improved things for a lot of Mac users, and I'm planning to write up a more comprehensive list of supported machines in the Debian wiki (for now).

There's now no need to use any of the older test installer images - please switch to RC2 for now. See http://cdimage.debian.org/cdimage/jessie_di_rc2/ for the images. If you want to install a 64-bit system with the 32-bit UEFI support, make sure you use the multi-arch amd64/i386 netinst or DVD. Otherwise, any of the standard i386 images should work for a 32-bit only system.

Upstreaming

My kernel patch to add the new /sys file was accepted upstream a while back, and has been in Linus' master branch for some time. It'll be in 4.0 unless something goes horribly wrong, and as it's such a tiny piece of code it's trivial to backport to anything remotely recent too.

I've also just seen that my patch for grub2 to use this new /sys file has been accepted upstream this week. Again, the change is small and self-contained so should be easy to copy across into other trees too.

Mixed EFI systems should now have better support across all distros in the near future, I hope.

02:44 :: # :: /debian/CDs :: 11 comments

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Re: Re: UEFI Debian installer work for Jessie, part 6
Steve wrote on Mon, 30 Mar 2015 16:09

One of the problems with a mixed EFI system is that there is no easy way for userland programs to know whether they're running on top of a 32-bit EFI or a 64-bit EFI firmware. Clearly, most programs don't need to know! But there's a small set that do care, specifically boot loader installation programs like grub-install; it needs to know whether to generate and install grubx64.efi or grubia32.efi to make the system bootable.

The kernel already knows whether the underlying EFI firmware is 32- or 64-bit, so we just needed an extra interface to share that information with userland. I've added a tiny patch to create a new /sys file, following the style of the existing EFI kernel interfaces:

root@x205ta:/# cat /sys/firmware/efi/fw_platform_size
32

For what it's worth, the patch is at http://article.gmane.org/gmane.linux.kernel.efi/5229 and the corresponding patch for grub2 is at http://git.savannah.gnu.org/cgit/grub.git/commit/?id=1a33de8b5612f8d7ab344546f8a91fa814f712b5.

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