tools/trace: Quick instructions/notes.

Reviewed-by: Brian Paul <brianp@vmware.com>

src/gallium/tools/trace/README.txt

@@ -0,0 +1,39 @@
+These directory contains tools for manipulating traces produced by the trace
+pipe driver.
+
+
+Most debug builds of state trackers already load the trace driver by default.
+To produce a trace do
+
+  export GALLIUM_TRACE=foo.gtrace
+
+and run the application.  You can choose any name, but the .gtrace is
+recommended to avoid confusion with the .trace produced by apitrace.
+
+
+You can dump a trace by doing
+
+  ./dump.py foo.gtrace | less
+
+
+You can dump a JSON file describing the static state at any given draw call
+(e.g., 12345) by
+doing
+
+  ./dump_state.py -v -c 12345 foo.gtrace > foo.json
+
+or by specifying the n-th (e.g, 1st) draw call by doing
+
+  ./dump_state.py -v -d 1 foo.gtrace > foo.json
+
+The state is derived from the call sequence in the trace file, so no dynamic
+(eg. rendered textures) is included.
+
+
+You can compare two JSON files by doing
+
+  ./diff_state.py foo.json boo.json | less
+
+If you're investigating a regression in a state tracker, you can obtain a good
+and bad trace, dump respective state in JSON, and then compare the states to
+identify the problem.

src/gallium/tools/trace/TODO.txt

@@ -0,0 +1,9 @@
+* track more state
+
+  * constant buffers
+
+* organize state better (e.g., group stuff according to the place in the
+  pipeline)
+
+* write an utility that generated a simple graw C code that matches a
+  state dump.