http://bugs.winehq.org/show_bug.cgi?id=21515
--- Comment #125 from Stefan Dösinger stefandoesinger@gmx.at 2010-03-09 12:37:04 --- You need this libdxtn library to enable s3tc support in Mesa, or force it on in driconf.
In general the radeon driver has no issue with the s3tc patent because it just passes the compressed data through from the app to the card and doesn't care about compressing or decompressing it. However, apps can request s3tc compression and decompression from opengl(upload uncompressed data to a s3tc texture or vice versa). The mesa people were considering a special "Only passthrough s3tc" extension for wine, but that won't work because Mesa might still have to decompress the texture in case it hits a software fallback somewhere.