[PATCH] ALSA: pcm: Fix mmap capability check

[Takashi Iwai]

On Fri, 30 Jul 2021 09:19:16 +0200,
Jaroslav Kysela wrote:
> 
> On 20. 07. 21 11:26, Takashi Iwai wrote:
> > The hw_support_mmap() doesn't cover all memory allocation types and
> > might use a wrong device pointer for checking the capability.
> > Check the all memory allocation types more completely.
> 
> This change breaks mmap for the snd-dummy driver (fake_buffer). It seems that
> we need this fix?
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 6a2971a7e6a1..09c0e2a6489c 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -246,7 +246,7 @@ static bool hw_support_mmap(struct snd_pcm_substream
> *substream)
>         if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
>                 return false;
> 
> -       if (substream->ops->mmap)
> +       if (substream->ops->mmap || substream->ops->page)
>                 return true;
> 
>         switch (substream->dma_buffer.dev.type) {

Yes, that would work.  Or allowing the mmap for unknown buffer type by
blindly relying to the hw.info flag.  But ops->page check looks
safer.

Care to submit a proper patch?  Thanks!


Takashi