Messages in this thread | | | Date | Thu, 10 Oct 2013 14:09:37 -0400 | From | Peter Jones <> | Subject | Re: [PATCH] x86/efi: Add EFI framebuffer earlyprintk support |
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On Thu, Oct 10, 2013 at 07:45:21PM +0200, Ingo Molnar wrote: > > * 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.
It's the thing being interpretted in arch/x86/boot/compressed/eboot.c in setup_gop() in the code that looks like:
if (pixel_format == PIXEL_RGB_RESERVED_8BIT_PER_COLOR) { si->lfb_depth = 32; si->lfb_linelength = pixels_per_scan_line * 4; ... } else if (pixel_format == PIXEL_BGR_RESERVED_8BIT_PER_COLOR) { ... } else if (pixel_format == PIXEL_BIT_MASK) { find_bits(pixel_info.red_mask, &si->red_pos, &si->red_size); ... ...
> How are those mask values to be interpreted? As regular bitmasks? Are bits > in the masks set to 1 consecutively, starting from bit 0?
So, the spec actually has some sample code in it:
INTN GetPixelElementSize ( IN EFI_PIXEL_BITMASK *PixelBits ) { INTN HighestPixel = -1; INTN BluePixel; INTN RedPixel; INTN GreenPixel; INTN RsvdPixel; BluePixel = FindHighestSetBit (PixelBits->BlueMask); RedPixel = FindHighestSetBit (PixelBits->RedMask); GreenPixel = FindHighestSetBit (PixelBits->GreenMask); RsvdPixel = FindHighestSetBit (PixelBits->ReservedMask); HighestPixel = max (BluePixel, RedPixel); HighestPixel = max (HighestPixel, GreenPixel); HighestPixel = max (HighestPixel, RsvdPixel); return HighestPixel; } EFI_PHYSICAL_ADDRESS NewPixelAddress; EFI_PHYSICAL_ADDRESS CurrentPixelAddress; EFI_GRAPHICS_OUTPUT_MODE_INFORMATION OutputInfo; INTN PixelElementSize;
switch (OutputInfo.PixelFormat) { case PixelBitMask: PixelElementSize = GetPixelElementSize (&OutputInfo.PixelInformation); break; case PixelBlueGreenRedReserved8BitPerColor: case PixelRedGreenBlueReserved8BitPerColor: PixelElementSize = sizeof (EFI_GRAPHICS_OUTPUT_BLT_PIXEL); break; }
Which makes this painfully clear.
> 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?
Yes, 32 on almost all systems that implement a framebuffer console at all.
-- Peter
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