[alsa-devel] [PATCH] alsa-lib: update linked hw_ptr and appl_ptr

[Takashi Iwai]

On Fri, 25 Nov 2016 11:25:05 +0100,
sutar.mounesh at gmail.com wrote:
> 
> From: Andreas Pape <apape at de.adit-jv.com>
> 
> Plugin file provides no private hw_ptr and appl_ptr but instead links them to the slave pcm.
> If the slave pcm itself changes its hw_ptr or app_prt this needs to be done in file plugin, too.
> Plugin 'plug' is such a candidate changing the hw_ptr and app_ptr in hw_params call dependent on the automatically inserted plugins.
> ALSA unfortunately has no support for automatically updating chained pointers.
> A notification on pointer change seems to be prepared inside the snd_pcm_set_ptr() routine via
> rbptr->changed(), but it is not (yet) implemented so that we need to care for it manually.
> 
> Signed-off-by: Andreas Pape <apape at de.adit-jv.com>

Judging from the description, isn't it a generic problem, not specific
to file plugin?


thanks,

Takashi

> ---
>  src/pcm/pcm_file.c |    8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/src/pcm/pcm_file.c b/src/pcm/pcm_file.c
> index fec76eb..1e3d35b 100644
> --- a/src/pcm/pcm_file.c
> +++ b/src/pcm/pcm_file.c
> @@ -634,6 +634,14 @@ static int snd_pcm_file_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
>  			return err;
>  		}
>  	}
> +
> +	/* pointer may have changed - e.g if plug is used. */
> +	snd_pcm_unlink_hw_ptr(pcm, file->gen.slave);
> +	snd_pcm_unlink_appl_ptr(pcm, file->gen.slave);
> +
> +	snd_pcm_link_hw_ptr(pcm, file->gen.slave);
> +	snd_pcm_link_appl_ptr(pcm, file->gen.slave);
> +
>  	return 0;
>  }
>  
> -- 
> 1.7.9.5
>