[Mesa-dev] [PATCH v2 3/9] i915: Use L8A8 instead of I8 to simulate A8 on gen2

[ville.syrjala at linux.intel.com]

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.

v2: Handle the fallback in _mesa_choose_tex_format() and also
    do it for all alpha formats that currently accept A8

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/main/texformat.c                 | 3 +++
 3 files changed, 5 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/main/texformat.c b/src/mesa/main/texformat.c
index c61a748..f414ea3 100644
--- a/src/mesa/main/texformat.c
+++ b/src/mesa/main/texformat.c
@@ -155,12 +155,14 @@ _mesa_choose_tex_format(struct gl_context *ctx, GLenum target,
    case GL_ALPHA4:
    case GL_ALPHA8:
       RETURN_IF_SUPPORTED(MESA_FORMAT_A_UNORM8);
+      RETURN_IF_SUPPORTED(MESA_FORMAT_L8A8_UNORM);
       break;
 
    case GL_ALPHA12:
    case GL_ALPHA16:
       RETURN_IF_SUPPORTED(MESA_FORMAT_A_UNORM16);
       RETURN_IF_SUPPORTED(MESA_FORMAT_A_UNORM8);
+      RETURN_IF_SUPPORTED(MESA_FORMAT_L8A8_UNORM);
       break;
 
    /* Luminance formats */
@@ -224,6 +226,7 @@ _mesa_choose_tex_format(struct gl_context *ctx, GLenum target,
 
    case GL_COMPRESSED_ALPHA_ARB:
       RETURN_IF_SUPPORTED(MESA_FORMAT_A_UNORM8);
+      RETURN_IF_SUPPORTED(MESA_FORMAT_L8A8_UNORM);
       break;
    case GL_COMPRESSED_LUMINANCE_ARB:
       RETURN_IF_SUPPORTED(MESA_FORMAT_L_UNORM8);
-- 
1.8.5.5