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
