On Fri, Aug 22, 2008 at 08:07:44AM +0200, Takashi Iwai wrote: > I don't think that this must work for *every* platform, too, and it's > not expected from the driver. The systems without uncached memory > access can simply return an error from dma_mmap_coherent() call, so > that the driver can disable the mmap. That'd be enough. true, I've used snd_pcm_indirect for HAL2 driver, which works even on SGI IP28 machines. > Now, how to handle these exceptions: a question comes into my mind > again -- how does the framebuffer handle these as well? most framebuffers have a dedicated set of video memory and this memory is just mmaped uncached either via TLB/MMU (MIPS) or rules inside the system (PARISC uses IO space memory, which is always uncached). The code which does this mmaping is in drivers/video/fbmem.c plus fb_pgprotect out of an include/asm header file. For framebuffers without dedicated video memory the memory is mmaped write through or uncached. A driver, which uses this, is drivers/video/gbefb.c. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessary a good idea. [ RFC1925, 2.3 ]
