+
+
+<h2>Gallium environment variables</h2>
+
+<ul>
+<li>GALLIUM_HUD - draws various information on the screen, like framerate,
+ cpu load, driver statistics, performance counters, etc.
+ Set GALLIUM_HUD=help and run e.g. glxgears for more info.
+<li>GALLIUM_HUD_PERIOD - sets the hud update rate in seconds (float). Use zero
+ to update every frame. The default period is 1/2 second.
+<li>GALLIUM_HUD_VISIBLE - control default visibility, defaults to true.
+<li>GALLIUM_HUD_TOGGLE_SIGNAL - toggle visibility via user specified signal.
+ Especially useful to toggle hud at specific points of application and
+ disable for unencumbered viewing the rest of the time. For example, set
+ GALLIUM_HUD_VISIBLE to false and GALLIUM_HUD_TOGGLE_SIGNAL to 10 (SIGUSR1).
+ Use kill -10 <pid> to toggle the hud as desired.
+<li>GALLIUM_HUD_DUMP_DIR - specifies a directory for writing the displayed
+ hud values into files.
+<li>GALLIUM_DRIVER - useful in combination with LIBGL_ALWAYS_SOFTWARE=true for
+ choosing one of the software renderers "softpipe", "llvmpipe" or "swr".
+<li>GALLIUM_LOG_FILE - specifies a file for logging all errors, warnings, etc.
+ rather than stderr.
+<li>GALLIUM_PRINT_OPTIONS - if non-zero, print all the Gallium environment
+ variables which are used, and their current values.
+<li>GALLIUM_DUMP_CPU - if non-zero, print information about the CPU on start-up
+<li>TGSI_PRINT_SANITY - if set, do extra sanity checking on TGSI shaders and
+ print any errors to stderr.
+<LI>DRAW_FSE - ???
+<LI>DRAW_NO_FSE - ???
+<li>DRAW_USE_LLVM - if set to zero, the draw module will not use LLVM to execute
+ shaders, vertex fetch, etc.
+<li>ST_DEBUG - controls debug output from the Mesa/Gallium state tracker.
+Setting to "tgsi", for example, will print all the TGSI shaders.
+See src/mesa/state_tracker/st_debug.c for other options.
+</ul>
+
+<h3>Clover state tracker environment variables</h3>
+
+<ul>
+<li>CLOVER_EXTRA_BUILD_OPTIONS - allows specifying additional compiler and linker
+ options. Specified options are appended after the options set by the OpenCL
+ program in clBuildProgram.
+<li>CLOVER_EXTRA_COMPILE_OPTIONS - allows specifying additional compiler
+ options. Specified options are appended after the options set by the OpenCL
+ program in clCompileProgram.
+<li>CLOVER_EXTRA_LINK_OPTIONS - allows specifying additional linker
+ options. Specified options are appended after the options set by the OpenCL
+ program in clLinkProgram.
+</ul>
+
+
+<h3>Softpipe driver environment variables</h3>
+<ul>
+<li>SOFTPIPE_DUMP_FS - if set, the softpipe driver will print fragment shaders
+ to stderr
+<li>SOFTPIPE_DUMP_GS - if set, the softpipe driver will print geometry shaders
+ to stderr
+<li>SOFTPIPE_NO_RAST - if set, rasterization is no-op'd. For profiling purposes.
+<li>SOFTPIPE_USE_LLVM - if set, the softpipe driver will try to use LLVM JIT for
+ vertex shading processing.
+</ul>
+
+
+<h3>LLVMpipe driver environment variables</h3>