[Mesa-dev] [PATCH] st/dri: remove GALLIUM_MSAA and __GL_FSAA_MODE environment variables

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

Some users don't understand that these variables can break OpenGL.
The general is rule is that if an app supports MSAA, you mustn't use
GALLIUM_MSAA.

For example, if an app has an 8xMSAA FBO and GALLIUM_MSAA=4
is set, resolving the FBO to the back buffer will be rejected which will look
like this on all gallium drivers:

http://www.phoronix.com/scan.php?page=article&item=amd_radeonsi_msaa

The environment variables also have no effect on modern apps like TF2, but
there is still a performance hit due to wasted bandwidth and VRAM.

In a nutshell, it does more harm than good.

Cc: 10.2 10.3 <mesa-stable at lists.freedesktop.org>
---
 src/gallium/state_trackers/dri/dri_screen.c | 35 -----------------------------
 1 file changed, 35 deletions(-)

diff --git a/src/gallium/state_trackers/dri/dri_screen.c b/src/gallium/state_trackers/dri/dri_screen.c
index fdcedcb..9cdebf8 100644
--- a/src/gallium/state_trackers/dri/dri_screen.c
+++ b/src/gallium/state_trackers/dri/dri_screen.c
@@ -227,37 +227,6 @@ dri_fill_in_modes(struct dri_screen *screen)
    return (const __DRIconfig **)configs;
 }
 
-/* The Gallium way to force MSAA. */
-DEBUG_GET_ONCE_NUM_OPTION(msaa, "GALLIUM_MSAA", 0);
-
-/* The NVIDIA way to force MSAA. The same variable is used by the NVIDIA
- * driver. */
-DEBUG_GET_ONCE_NUM_OPTION(msaa_nv, "__GL_FSAA_MODE", 0);
-
-static void
-dri_force_msaa_visual(struct st_visual *stvis,
-                      struct pipe_screen *screen)
-{
-   int i;
-   int samples = debug_get_option_msaa();
-
-   if (!samples)
-      samples = debug_get_option_msaa_nv();
-
-   if (samples <= 1)
-      return; /* nothing to do */
-
-   /* Choose a supported sample count greater than or equal to samples. */
-   for (i = samples; i <= MSAA_VISUAL_MAX_SAMPLES; i++) {
-      if (screen->is_format_supported(screen, stvis->color_format,
-                                      PIPE_TEXTURE_2D, i,
-                                      PIPE_BIND_RENDER_TARGET)) {
-         stvis->samples = i;
-         break;
-      }
-   }
-}
-
 /**
  * Roughly the converse of dri_fill_in_modes.
  */
@@ -282,10 +251,6 @@ dri_fill_st_visual(struct st_visual *stvis, struct dri_screen *screen,
    if (mode->sampleBuffers) {
       stvis->samples = mode->samples;
    }
-   else {
-      /* This must be done after stvis->color_format is set. */
-      dri_force_msaa_visual(stvis, screen->base.screen);
-   }
 
    switch (mode->depthBits) {
    default:
-- 
1.9.1