On Thu, Oct 10, 2013 at 07:45:21PM +0200, Ingo Molnar wrote:
>
> * Peter Jones <pjo...@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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