Dri2 buffer format

[Russell Shaw]

Hi,
How should the "format" of a DRI2 buffer be determined?


http://www.x.org/releases/current/doc/dri2proto/dri2proto.txt

DRI2ATTACH_FORMAT { attachment: CARD32
             format:     CARD32 }

     The DRI2ATTACH_FORMAT describes an attachment and the associated
     format.  'attachment' describes the attachment point for the buffer,
     'format' describes an opaque, device-dependent format for the buffer.


xorg-server-1.7.7/hw/xfree86/dri2/dri2ext.c


If it's opaque, how does a user or library know what bytes are red/green/blue
so that you can draw a line in the right colour?