[U-Boot] [PATCH] efi_loader: Fix GOP 32bpp exposure

[Heinrich Schuchardt]

On 06/19/2018 01:47 PM, Alexander Graf wrote:
> We store pixels as BGRA in memory, as can be seen from struct efi_gop_pixel.
> So we need to expose the same format to UEFI payloads to actually have them
> use the correct colors.
> 
> Reported-by: Fabian Vogt <fvogt at suse.com>
> Signed-off-by: Alexander Graf <agraf at suse.de>
> ---
>  lib/efi_loader/efi_gop.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/efi_loader/efi_gop.c b/lib/efi_loader/efi_gop.c
> index 1afe8418e1..3a36bbcbfa 100644
> --- a/lib/efi_loader/efi_gop.c
> +++ b/lib/efi_loader/efi_gop.c
> @@ -472,7 +472,7 @@ efi_status_t efi_gop_register(void)
>  	gopobj->info.version = 0;
>  	gopobj->info.width = col;
>  	gopobj->info.height = row;
> -	gopobj->info.pixel_format = EFI_GOT_RGBA8;
> +	gopobj->info.pixel_format = EFI_GOT_BGRA8;

Graphic cards have been produced both with RGB and BRG bit sequence.

According to the VESA BIOS Extension Core Functions Standard 2.0
describe a pixel we need the RedFieldPosition, GreenFieldPosition,
BlueFieldPosition, and RsvdFieldPosition fields as well as RedMaskSize,
GreenMaskSize, BlueMaskSize, and RsvdMaskSize.

For the EFI implementation we only have to consider a low endian memory
model.

Currently in drivers/video/vidconsole-uclass.c we make the following
assumptions:

16bit graphic cards have
red in bits 11..15
green in bits 5..10
blue in bis 0..4

32bit graphic cards have
red in bits 16..23
green in bits 8..15
blue in bis 0..7

of an u16 or u32 pixel.

In efi_vid16_to_blt_col() we make the same assumption.

Structure efi_gop_pixel has sequence blue, green, red, reserved which
matches the 32bit assumption in drivers/video/vidconsole-uclass.c.

struct efi_gop_pixel {
        u8 blue;
        u8 green;
        u8 red;
        u8 reserved;
};

So setting pixel_format = EFI_GOT_BGRA8 provides consistency in our
implementation but will fail on RGBA graphic cards.

@Anatolij:
Do you have an overview if we have blue in the low bits of the pixels in
all low endian U-Boot supported devices?

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

>  	gopobj->info.pixels_per_scanline = col;
>  
>  	gopobj->bpix = bpix;
>