[alsa-devel] [PATCH 2/4] pcm: rate: add rewindable and forwardable callbacks

[Jaroslav Kysela]

Date 12.6.2014 12:34, Alexander E. Patrakov wrote:
> This commit does not fix nonsense values returned by the rewind and
> forward callbacks. E.g., with period_size = 1024 and buffer_size = 4096,
> an attempt to rewind 1024 samples from the nearly-full buffer returns
> 4090.
> 
> Due to these nonsense values, the current rate plugin should be treated
> as non-rewindable. That's why the new callbacks return 0.
> 
> Signed-off-by: Alexander E. Patrakov <patrakov at gmail.com>

I don't agree. The snd_pcm_rate_move_applptr() should be fixed instead
this blocking attempt. Do you have any simple use case?

                                       Jaroslav

> ---
>  src/pcm/pcm_rate.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c
> index 2eb4b1b..58ed842 100644
> --- a/src/pcm/pcm_rate.c
> +++ b/src/pcm/pcm_rate.c
> @@ -689,6 +689,16 @@ static int snd_pcm_rate_reset(snd_pcm_t *pcm)
>  	return 0;
>  }
>  
> +static snd_pcm_sframes_t snd_pcm_rate_rewindable(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
> +{
> +	return 0;
> +}
> +
> +static snd_pcm_sframes_t snd_pcm_rate_forwardable(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
> +{
> +	return 0;
> +}
> +
>  static snd_pcm_sframes_t snd_pcm_rate_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
>  {
>  	snd_pcm_rate_t *rate = pcm->private_data;
> @@ -1221,7 +1231,9 @@ static const snd_pcm_fast_ops_t snd_pcm_rate_fast_ops = {
>  	.drop = snd_pcm_generic_drop,
>  	.drain = snd_pcm_rate_drain,
>  	.pause = snd_pcm_generic_pause,
> +	.rewindable = snd_pcm_rate_rewindable,
>  	.rewind = snd_pcm_rate_rewind,
> +	.forwardable = snd_pcm_rate_forwardable,
>  	.forward = snd_pcm_rate_forward,
>  	.resume = snd_pcm_generic_resume,
>  	.writei = snd_pcm_mmap_writei,
> 


-- 
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project; Red Hat, Inc.