I tried changing the return for case BITSPIXEL in X11DRV_GetDeviceCaps, and now I get all sorts of errors from X11DRV_CreateBitmap: Trying to make bitmap with planes=1, bpp=32
Oh well, submit your patch as it is now. The 24 / 32 'problem' needs a specific fix anyway.
A work around for the issue would be to essentially consider 24 and 32 modes as identical in your code (this way one is sure to never 'accidently' refuse a mode due to this feature).
Lionel