ALSA: pcm: Check mmap capability of runtime dma buffer at first
Currently we check only the substream->dma_buffer as the preset of the
buffer configuration for verifying the availability of mmap. But a
few drivers rather set up the buffer in the own way without the
standard buffer preallocation using substream->dma_buffer, and they
miss the proper checks. (Now it's working more or less fine as most
of them are running only on x86).
Actually, they may set up the runtime dma_buffer (referred via
snd_pcm_get_dma_buf()) at the open callback, though. That is, this
could have been used as the primary source.
This patch changes the hw_support_mmap() function to check the runtime
dma buffer at first. It's usually NULL with the standard buffer
preallocation, and in that case, we continue checking
substream->dma_buffer as fallback.
Link: https://lore.kernel.org/r/20210809071829.22238-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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