[alsa-devel] [PATCH RFC 6/9] ALSA: core: pass audio tstamp config from userspace

[Takashi Iwai]

At Mon,  8 Dec 2014 16:23:43 -0600,
Pierre-Louis Bossart wrote:
> 
> Let userspace select audio timestamp config, ignore and zero all
> other fields
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
>  sound/core/pcm_native.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 37a7137..7dcd6bd 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -706,6 +706,7 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
>  	struct snd_pcm_runtime *runtime = substream->runtime;
>  
>  	snd_pcm_stream_lock_irq(substream);
> +	memset(status, 0, sizeof(*status));

This memset() can be outside the lock.

>  	status->state = runtime->status->state;
>  	status->suspended_state = runtime->status->suspended_state;
>  	if (status->state == SNDRV_PCM_STATE_OPEN)
> @@ -757,7 +758,8 @@ static int snd_pcm_status_user(struct snd_pcm_substream *substream,
>  	struct snd_pcm_status status;
>  	int res;
>  	
> -	memset(&status, 0, sizeof(status));
> +	if (copy_from_user(&status, _status, sizeof(status)))
> +		return -EFAULT;
>  	res = snd_pcm_status(substream, &status);

You're clearing the data at the beginning of snd_pcm_status(), so it
doesn't make sense to do copy_from_user().

In anyway, I prefer passing the extra argument for the parameter user
may set instead of initializing the whole struct beforehand.
snd_pcm_status() is called only internally, so it's no big problem to
change the arguments.


Takashi