Re: [PATCH] x86/efi: Add EFI framebuffer earlyprintk support

[Ingo Molnar <mingo@kernel.org>]

* Peter Jones <pjones@redhat.com> wrote:

> On Thu, Oct 10, 2013 at 07:28:44PM +0200, Ingo Molnar wrote:
> > 
> > Is a non-32-bit framebuffer a possibility? If yes then it might be nice to 
> > emit an informative printk() here, so that users who try to enable EFI 
> > early-printk can at least see why it's not working. (Assuming they get to 
> > look at regular printk output, on a safe/working kernel.)
> 
> Not really - the spec allows RGBx, BGRx, and for custom bit masks, but
> they're define like:
> 
> typedef struct {
> 	UINT32 RedMask;
> 	UINT32 GreenMask;
> 	UINT32 BlueMask;
> 	UINT32 ReservedMask;
> } EFI_PIXEL_BITMASK;

Hm, that structure does not show up anywhere in the kernel that I can see.

How are those mask values to be interpreted? As regular bitmasks? Are bits 
in the masks set to 1 consecutively, starting from bit 0?

Also, the main question would be, what is the typical value for 
si->lfb_depth. 32 on almost all EFI systems? All around the map? Depends 
on what graphics state the EFI bootloader passes us?

Thanks,

	Ingo