3 files changed, 20 insertions, 2 deletions
diff --git a/src/gallium/state_trackers/dri/common/dri_context.c b/src/gallium/state_trackers/dri/common/dri_context.c
index 5794e487158..ab80fc75bd4 100644
--- a/src/gallium/state_trackers/dri/common/dri_context.c
+++ b/src/gallium/state_trackers/dri/common/dri_context.c
@@ -58,6 +58,8 @@ static void dri_fill_st_options(struct st_config_options *options,
       driQueryOptionb(optionCache, "disable_glsl_line_continuations");
    options->disable_blend_func_extended =
       driQueryOptionb(optionCache, "disable_blend_func_extended");
+   options->force_s3tc_enable =
+      driQueryOptionb(optionCache, "force_s3tc_enable");
 }
 
 GLboolean
diff --git a/src/gallium/state_trackers/dri/common/dri_screen.c b/src/gallium/state_trackers/dri/common/dri_screen.c
index c8aed63f1d3..ca17742eb5b 100644
--- a/src/gallium/state_trackers/dri/common/dri_screen.c
+++ b/src/gallium/state_trackers/dri/common/dri_screen.c
@@ -41,6 +41,7 @@
 #include "state_tracker/drm_driver.h"
 
 #include "util/u_debug.h"
+#include "util/u_format_s3tc.h"
 
 #define MSAA_VISUAL_MAX_SAMPLES 32
 
@@ -54,7 +55,7 @@ PUBLIC const char __driConfigOptions[] =
       DRI_CONF_SECTION_END
 
       DRI_CONF_SECTION_QUALITY
-/*       DRI_CONF_FORCE_S3TC_ENABLE("false") */
+         DRI_CONF_FORCE_S3TC_ENABLE("false")
          DRI_CONF_PP_CELSHADE(0)
          DRI_CONF_PP_NORED(0)
          DRI_CONF_PP_NOGREEN(0)
@@ -76,7 +77,7 @@ PUBLIC const char __driConfigOptions[] =
 
 #define false 0
 
-static const uint __driNConfigOptions = 12;
+static const uint __driNConfigOptions = 13;
 
 static const __DRIconfig **
 dri_fill_in_modes(struct dri_screen *screen)
@@ -416,6 +417,20 @@ dri_init_screen_helper(struct dri_screen *screen,
                        screen->sPriv->myNum,
                        driver_descriptor.name);
 
+   /* Handle force_s3tc_enable. */
+   if (!util_format_s3tc_enabled &&
+       driQueryOptionb(&screen->optionCache, "force_s3tc_enable")) {
+      /* Ensure libtxc_dxtn has been loaded if available.
+       * Forcing S3TC on before calling this would prevent loading
+       * the library.
+       * This is just a precaution, the driver should have called it
+       * already.
+       */
+      util_format_s3tc_init();
+
+      util_format_s3tc_enabled = TRUE;
+   }
+
    return dri_fill_in_modes(screen);
 }
 
diff --git a/src/gallium/state_trackers/osmesa/osmesa.c b/src/gallium/state_trackers/osmesa/osmesa.c
index 5908316dc81..594372bd725 100644
--- a/src/gallium/state_trackers/osmesa/osmesa.c
+++ b/src/gallium/state_trackers/osmesa/osmesa.c
@@ -545,6 +545,7 @@ OSMesaCreateContextExt(GLenum format, GLint depthBits, GLint stencilBits,
    attribs.options.force_glsl_extensions_warn = FALSE;
    attribs.options.disable_blend_func_extended = FALSE;
    attribs.options.disable_glsl_line_continuations = FALSE;
+   attribs.options.force_s3tc_enable = FALSE;
 
    osmesa_init_st_visual(&attribs.visual,
                          PIPE_FORMAT_R8G8B8A8_UNORM,