[alsa-devel] [PATCH for-4.11] ASoC: don't dereference NULL pcm_{new, free}

[Kuninori Morimoto]

Hi Brian

Thank you for your patch

> Not all platform drivers have pcm_{new,free} callbacks. Seen with a
> "snd-soc-dummy" codec from sound/soc/rockchip/rk3399_gru_sound.c.
(snip)
> Fixes: 99b04f4c4051 ("ASoC: add Component level pcm_new/pcm_free")
> Signed-off-by: Brian Norris <briannorris at chromium.org>
> ---
> I'm really not that familiar with this subsystem... but this does fix the
> crash seen here.
> 
>  sound/soc/soc-core.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index 6dca408faae3..2722bb0c5573 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -3326,7 +3326,10 @@ static int snd_soc_platform_drv_pcm_new(struct snd_soc_pcm_runtime *rtd)
>  {
>  	struct snd_soc_platform *platform = rtd->platform;
>  
> -	return platform->driver->pcm_new(rtd);
> +	if (platform->driver->pcm_new)
> +		return platform->driver->pcm_new(rtd);
> +	else
> +		return 0;
>  }
>  
>  static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
> @@ -3334,7 +3337,8 @@ static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
>  	struct snd_soc_pcm_runtime *rtd = pcm->private_data;
>  	struct snd_soc_platform *platform = rtd->platform;
>  
> -	platform->driver->pcm_free(pcm);
> +	if (platform->driver->pcm_free)
> +		platform->driver->pcm_free(pcm);
>  }

It is a littlle bit strange for me.
commit 99b04f4c4051 has below code. This means, if platform doesn't have pcm_new/free callback,
component doesn't have snd_soc_platform_drv_pcm_new/free.
But your case, platform doesn't have pcm_new/free, but component had it ?

...
@@ -3181,6 +3198,10 @@ int snd_soc_add_platform(struct device *dev, struct snd_soc_platform *platform,
 		platform->component.probe = snd_soc_platform_drv_probe;
 	if (platform_drv->remove)
 		platform->component.remove = snd_soc_platform_drv_remove;
+	if (platform_drv->pcm_new)
+		platform->component.pcm_new = snd_soc_platform_drv_pcm_new;
+	if (platform_drv->pcm_free)
+		platform->component.pcm_free = snd_soc_platform_drv_pcm_free;
 
 #ifdef CONFIG_DEBUG_FS
 	platform->component.debugfs_prefix = "platform";