[Mesa-dev] [PATCH] mesa: Match MESA_FORMAT_B5G6R5 for a shallow pixel format of GL_RGB

[Erik Faye-Lund]

On Thu, Sep 3, 2015 at 6:05 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> If the user supplies a pixel format of GL_RGB + GL_UNSIGNED_SHORT_5_6_5
> and specifies a generic unsized GL_RGB internal format, match that to a
> texture format of MESA_FORMAT_B5G6R5 if supported by the hardware.
>
> Noticed while playing with mesa-demos/teximage:
>
>   TexImage(RGB/565 256 x 256): 79.8 images/sec, 10.0 MB/sec
>   TexSubImage(RGB/565 256 x 256): 3804.9 images/sec, 475.6 MB/sec
>   GetTexImage(RGB/565 256 x 256): 99.5 images/sec, 12.4 MB/sec
>
> becomes
>
>   TexImage(RGB/565 256 x 256): 3439.1 images/sec, 429.9 MB/sec
>   TexSubImage(RGB/565 256 x 256): 3744.1 images/sec, 468.0 MB/sec
>   GetTexImage(RGB/565 256 x 256): 4713.5 images/sec, 589.2 MB/sec
>
> on a puny Baytrail which is still far from what it is capable of. The
> reason for the disparity is that the teximage demo uses a busy texture
> which is performs an accelerated pixel conversion from the user's B5G6R5
> into the native X8B8G8R8. After the patch, no conversion is required
> allowing use of the blitter and memcpy fast paths.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  src/mesa/main/texformat.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/src/mesa/main/texformat.c b/src/mesa/main/texformat.c
> index fd9f335..866c7b3 100644
> --- a/src/mesa/main/texformat.c
> +++ b/src/mesa/main/texformat.c
> @@ -114,6 +114,8 @@ _mesa_choose_tex_format(struct gl_context *ctx, GLenum target,
>     case GL_RGB:
>        if (type == GL_UNSIGNED_INT_2_10_10_10_REV) {
>           RETURN_IF_SUPPORTED(MESA_FORMAT_B10G10R10A2_UNORM);
> +      } else if (type == GL_UNSIGNED_SHORT_5_6_5) {
> +         RETURN_IF_SUPPORTED(MESA_FORMAT_B5G6R5_UNORM);

Shouldn't this be MESA_FORMAT_R5G6B5_UNORM? AFAICT, the reason for
using BGR above, is the _REV suffix on the type...