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. But how do I get at a suitable struct device in hw_support_mmap()?
