[Mesa-dev] [PATCH 3/9] i915: Use L8A8 instead of I8 to simulate A8 on gen2

[Eric Anholt]

ville.syrjala at linux.intel.com writes:

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Gen2 doesn't support the A8 texture format. Currently the driver
> substitutes it with I8, but that results in incorrect RGB values.
> Use A8L8 instead. We end up wasting a bit of memory, but at least
> we should get the correct results.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72819
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80050
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38873
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  src/mesa/drivers/dri/i915/i830_texstate.c   |  2 --
>  src/mesa/drivers/dri/i915/i915_context.c    |  3 ++-
>  src/mesa/drivers/dri/i915/intel_tex_image.c | 22 ++++++++++++++++++++++
>  3 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i915/i830_texstate.c b/src/mesa/drivers/dri/i915/i830_texstate.c
> index 58d3356..b1414c7 100644
> --- a/src/mesa/drivers/dri/i915/i830_texstate.c
> +++ b/src/mesa/drivers/dri/i915/i830_texstate.c
> @@ -47,8 +47,6 @@ translate_texture_format(GLuint mesa_format)
>        return MAPSURF_8BIT | MT_8BIT_L8;
>     case MESA_FORMAT_I_UNORM8:
>        return MAPSURF_8BIT | MT_8BIT_I8;
> -   case MESA_FORMAT_A_UNORM8:
> -      return MAPSURF_8BIT | MT_8BIT_I8; /* Kludge! */
>     case MESA_FORMAT_L8A8_UNORM:
>        return MAPSURF_16BIT | MT_16BIT_AY88;
>     case MESA_FORMAT_B5G6R5_UNORM:
> diff --git a/src/mesa/drivers/dri/i915/i915_context.c b/src/mesa/drivers/dri/i915/i915_context.c
> index 7f43896..3fd571d 100644
> --- a/src/mesa/drivers/dri/i915/i915_context.c
> +++ b/src/mesa/drivers/dri/i915/i915_context.c
> @@ -109,7 +109,8 @@ intel_init_texture_formats(struct gl_context *ctx)
>     ctx->TextureFormatSupported[MESA_FORMAT_B5G5R5A1_UNORM] = true;
>     ctx->TextureFormatSupported[MESA_FORMAT_B5G6R5_UNORM] = true;
>     ctx->TextureFormatSupported[MESA_FORMAT_L_UNORM8] = true;
> -   ctx->TextureFormatSupported[MESA_FORMAT_A_UNORM8] = true;
> +   if (intel->gen == 3)
> +      ctx->TextureFormatSupported[MESA_FORMAT_A_UNORM8] = true;
>     ctx->TextureFormatSupported[MESA_FORMAT_I_UNORM8] = true;
>     ctx->TextureFormatSupported[MESA_FORMAT_L8A8_UNORM] = true;
>  
> diff --git a/src/mesa/drivers/dri/i915/intel_tex_image.c b/src/mesa/drivers/dri/i915/intel_tex_image.c
> index 57674b9..be9a4ff 100644
> --- a/src/mesa/drivers/dri/i915/intel_tex_image.c
> +++ b/src/mesa/drivers/dri/i915/intel_tex_image.c
> @@ -14,6 +14,7 @@
>  #include "main/texobj.h"
>  #include "main/teximage.h"
>  #include "main/texstore.h"
> +#include "main/texformat.h"
>  
>  #include "intel_context.h"
>  #include "intel_mipmap_tree.h"
> @@ -362,9 +363,30 @@ intel_image_target_texture_2d(struct gl_context *ctx, GLenum target,
>                                    image->tile_x, image->tile_y);
>  }
>  
> +static mesa_format intel_choose_tex_format(struct gl_context *ctx,
> +                                           GLenum target,
> +                                           GLint internalFormat,
> +                                           GLenum format, GLenum type)
> +{
> +   struct intel_context *intel = intel_context(ctx);
> +
> +   switch (internalFormat) {
> +   case GL_ALPHA:
> +   case GL_ALPHA4:
> +   case GL_ALPHA8:
> +      /* no A8 on gen2 :( */
> +      if (intel->gen == 2)
> +         return MESA_FORMAT_L8A8_UNORM;
> +      /* fall through */
> +   default:
> +      return _mesa_choose_tex_format(ctx, target, internalFormat, format, type);
> +   }
> +}

Instead, I'd rather see _mesa_choose_tex_format just grow another case:

      RETURN_IF_SUPPORTED(MESA_FORMAT_L8A8_UNORM);
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