Marek Olšák wrote on 2009-12-22 08:40:
> Hi,
>
> I noticed that gallium/auxiliary/util/u_format.csv contains some weird 
> swizzling, for example see this:
>
> $ grep zyxw u_format.csv
> PIPE_FORMAT_A8R8G8B8_UNORM        , arith , 1, 1, un8 , un8 , un8 , 
> un8 , zyxw, rgb
> PIPE_FORMAT_A1R5G5B5_UNORM        , arith , 1, 1, un5 , un5 , un5 , 
> un1 , zyxw, rgb
> PIPE_FORMAT_A4R4G4B4_UNORM        , arith , 1, 1, un4 , un4 , un4 , 
> un4 , zyxw, rgb
> PIPE_FORMAT_A8B8G8R8_SNORM        , arith , 1, 1, sn8 , sn8 , sn8 , 
> sn8 , zyxw, rgb
> PIPE_FORMAT_B8G8R8A8_SRGB         , arith , 1, 1, u8  , u8  , u8  , u8 
>  , zyxw, srgb
>
> It's hard to believe that ARGB, ABGR, and BGRA have the same 
> swizzling. Let's continue our journey:
>
> $ grep A8R8G8B8 u_format.csv
> PIPE_FORMAT_A8R8G8B8_UNORM        , arith , 1, 1, un8 , un8 , un8 , 
> un8 , zyxw, rgb
> PIPE_FORMAT_A8R8G8B8_SRGB         , arith , 1, 1, u8  , u8  , u8  , 
> u8  , wxyz, srgb
>
> Same formats, different swizzling? Also:
>
> $ grep B8G8R8A8 u_format.csv
> PIPE_FORMAT_B8G8R8A8_UNORM        , arith , 1, 1, un8 , un8 , un8 , 
> un8 , yzwx, rgb
> PIPE_FORMAT_B8G8R8A8_SRGB         , arith , 1, 1, u8  , u8  , u8  , 
> u8  , zyxw, srgb
>
> Same formats, different swizzling? I don't really get it. And there's 
> much more cases like these. Could someone tell me what the intended 
> order of channels should be? (or possibly propose a fix) The meaning 
> of the whole table is self-contradictory and it's definitely the 
> source of some r300g bugs.
>
Marek,

Yes, that seems like a defect. The format swizzle field tells us how to 
"swizzle" the incoming pixel so that its components are ordered in some 
predefined order. For RGB and SRGB colorspaces the order is R, G, B and 
A. For depth-stencil, ie. ZS color space the order is Z and then S.

I will have a look at this.

Thanks.

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