Loader: Reset EFI framebuffer state before kernel transition

[kevans]

Summary

Anything before this point can set the console into whatever mode/resolution it feels like. Lacking a better way to determine what the current geometry of the screen looks like, try and reset the screen using GOP to a good mode before we transition into the kernel. This puts the screen into a consistent state so that we can pass the correct framebuffer information into the kernel.

UGA reset is currently a nop.

[imp]

stand/efi/loader/bootinfo.c

282

Isn't this true also of armv7 and i386?

stand/efi/loader/framebuffer.c

444

There are complaints about it always picking the highest pixel count, since some are large and the font is tiny on them.

[imp]

stand/efi/loader/bootinfo.c

285

We should check the return status here and avoid calling efi_find_framebuffer()

[kevans]

stand/efi/loader/bootinfo.c

282

I'd have to double-check- that might now be true of all arch's that will compile EFI bits by default. I think @manu had recently stubbed out the struct efi_fb for armv7 at least.

[manu]

stand/efi/loader/bootinfo.c

282

Yeah armv7 and arm64 have the efi_fb in metadata.h (even if efifb still doesn't work).