ALSA: pcm: Fix mmap breakage without explicit buffer setup

The recent fix c4824ae7db41 ("ALSA: pcm: Fix mmap capability check")
restricts the mmap capability only to the drivers that properly set up
the buffers, but it caused a regression for a few drivers that manage
the buffer on its own way.

For those with UNKNOWN buffer type (i.e. the uninitialized / unused
substream->dma_buffer), just assume that the driver handles the mmap
properly and blindly trust the hardware info bit.

Fixes: c4824ae7db41 ("ALSA: pcm: Fix mmap capability check")
Reported-and-tested-by: Jeff Woods <jwoods@fnordco.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/s5him0gpghv.wl-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 09c0e2a..71323d8 100644 (file)
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -251,7 +251,10 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
 
        switch (substream->dma_buffer.dev.type) {
        case SNDRV_DMA_TYPE_UNKNOWN:
-               return false;
+               /* we can't know the device, so just assume that the driver does
+                * everything right
+                */
+               return true;
        case SNDRV_DMA_TYPE_CONTINUOUS:
        case SNDRV_DMA_TYPE_VMALLOC:
                return true;