[Mesa-dev] gallium endianness and hw drivers

[Michel Dänzer]

On Mit, 2014-01-15 at 14:27 +0100, Marek Olšák wrote:
> On Wed, Jan 15, 2014 at 7:07 AM, Michel Dänzer <michel at daenzer.net> wrote:
> > On Die, 2014-01-14 at 00:22 +0100, Marek Olšák wrote:
> >> I think the format conversion functions should look like:
> >>
> >> #ifdef BIG_ENDIAN
> >>    case PIPE_FORMAT_A8B8G8R8_UNORM:
> >>       return hw_format_for_R8G8B8A8_UNORM;
> >> ...
> >> #else
> >>    case PIPE_FORMAT_R8G8B8A8_UNORM:
> >>       return hw_format_for_R8G8B8A8_UNORM;
> >> #endif
> >>
> >> which can be simplified to:
> >>
> >>    case PIPE_FORMAT_RGBA8888_UNORM:
> >>       return hw_format_for_R8G8B8A8_UNORM;
> >>
> >> So that the GPU can see the same formats, but they are different for the CPU.
> >>
> >> What do you think?
> >
> > That might be an option, but PIPE_FORMAT_R8G8B8A8_UNORM is useful on big
> > endian hosts as well, e.g. it matches GL_RGBA / GL_UNSIGNED_BYTE
> > exactly.
> 
> I wouldn't worry about such optimizations when we don't even have
> proper big endian support.

I'd consider it part of proper big endian support though.


> I'd rather stick to the simplest solution for the old hardware.

What do you mean by old hardware? Remember that SI and newer have
basically no hardware byteswapping facilities anymore, and PowerPC
machines with PCIe slots are still being produced and sold.


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer