On Sat, 03 Aug 2019 12:30:24 +0200, Christoph Hellwig wrote: > > On Fri, Aug 02, 2019 at 10:24:02AM +0200, Takashi Iwai wrote: > > I wasn't careful enough to look at that change, sorry. > > > > The code there tries to check whether dma_mmap_coherent() would always > > fail on some platforms. Then the driver clears the mmap capability > > flag at the device open time and notifies user-space to fall back to > > the dumb read/write mode. > > > > So I'm afraid that simply dropping the check would cause the behavior > > regression, e.g. on PARISC. > > > > Is there any simple way to test whether dma_mmap_coherent() would work > > or not in general on the target platform? It's not necessarily in an > > ifdef at all. > > This isn't really a platform, but a per-device question. I can add a > "bool dma_can_mmap(struct device *dev)" helper to check that. Yes, this would fit perfect. > But how > do I get at a suitable struct device in hw_support_mmap()? substream->dma_buffer.dev.dev can be that, which is used in the mmap helper side, snd_pcm_lib_default_mmap(). Thanks! Takashi
