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+Debugging
+=========
+
+Debugging utilities in gallium.
+
+Debug Variables
+^^^^^^^^^^^^^^^
+
+All drivers respond to a set of common debug environment variables, as well as
+some driver-specific variables. Set them as normal environment variables for
+the platform or operating system you are running. For example, for Linux this
+can be done by typing "export var=value" into a console and then running the
+program from that console.
+
+Common
+""""""
+
+.. envvar:: GALLIUM_PRINT_OPTIONS <bool> (false)
+
+This option controls if the debug variables should be printed to stderr. This
+is probably the most useful variable, since it allows you to find which
+variables a driver uses.
+
+.. envvar:: GALLIUM_RBUG <bool> (false)
+
+Controls if the :ref:`rbug` should be used.
+
+.. envvar:: GALLIUM_TRACE <string> ("")
+
+If set, this variable will cause the :ref:`Trace` output to be written to the
+specified file. Paths may be relative or absolute; relative paths are relative
+to the working directory.  For example, setting it to "trace.xml" will cause
+the trace to be written to a file of the same name in the working directory.
+
+.. envvar:: GALLIUM_DUMP_CPU <bool> (false)
+
+Dump information about the current CPU that the driver is running on.
+
+.. envvar:: TGSI_PRINT_SANITY <bool> (false)
+
+Gallium has a built-in shader sanity checker.  This option controls whether
+the shader sanity checker prints its warnings and errors to stderr.
+
+.. envvar:: DRAW_USE_LLVM <bool> (false)
+
+Whether the :ref:`Draw` module will attempt to use LLVM for vertex and geometry shaders.
+
+
+State tracker-specific
+""""""""""""""""""""""
+
+.. envvar:: ST_DEBUG <flags> (0x0)
+
+Debug :ref:`flags` for the GL state tracker.
+
+
+Driver-specific
+"""""""""""""""
+
+.. envvar:: I915_DEBUG <flags> (0x0)
+
+Debug :ref:`flags` for the i915 driver.
+
+.. envvar:: I915_NO_HW <bool> (false)
+
+Stop the i915 driver from submitting commands to the hardware.
+
+.. envvar:: I915_DUMP_CMD <bool> (false)
+
+Dump all commands going to the hardware.
+
+.. envvar:: LP_DEBUG <flags> (0x0)
+
+Debug :ref:`flags` for the llvmpipe driver.
+
+.. envvar:: LP_NUM_THREADS <int> (number of CPUs)
+
+Number of threads that the llvmpipe driver should use.
+
+
+.. _flags:
+
+Flags
+"""""
+
+The variables of type "flags" all take a string with comma-separated flags to
+enable different debugging for different parts of the drivers or state
+tracker. If set to "help", the driver will print a list of flags which the
+variable accepts. Order does not matter.
+
+
+.. _rbug:
+
+Remote Debugger
+^^^^^^^^^^^^^^^
+
+The remote debugger, commonly known as rbug, allows for runtime inspections of
+:ref:`Context`, :ref:`Screen`, :ref:`Resource` and :ref:`Shader` objects; and
+pausing and stepping of :ref:`Draw` calls. Is used with rbug-gui which is
+hosted outside of the main mesa repository. rbug is can be used over a network
+connection, so the debugger does not need to be on the same machine.