Re: [PATCH 2/3 v2] ALSA: usb-audio: avoid setting of sample rate multiple times on bus

[Jiada Wang]

Hi Takashi

On 11/30/2016 05:51 PM, Takashi Iwai wrote:
> On Wed, 30 Nov 2016 08:59:22 +0100,
> Jiada Wang wrote:
> > From: Daniel Girnus <dgirnus@xxxxxxxxxxxxxx>
> >
> > ALSA usually calls the prepare function twice before starting the playback:
> > 1. On hw_params call from userland and
> > 2. internally when starting the stream.
> > Some device are not able to manage this and they will stop playback
> > if the sample rate will be configured several times over USB protocol.
> >
> > Signed-off-by: Jens Lorenz <jlorenz@xxxxxxxxxxxxxx>
> > Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
>
> The sign-off from Daniel seems missing?
>
> The code change looks OK, but it'd be nice to mention in the changelog
> that, after this patch, snd_usb_init_sample_rate() is still called
> properly whenever the parameter is changed since ep->need_setup_ep is
> set in snd_hsb_hw_params().
I will add missing sign-off and related information in changelog in v2

Thanks,
Jiada
> thanks,
>
> Takashi
>
> > ---
> >  sound/usb/pcm.c | 21 +++++++++++----------
> >  1 file changed, 11 insertions(+), 10 deletions(-)
> >
> > diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> > index 44d178e..a522c9a 100644
> > --- a/sound/usb/pcm.c
> > +++ b/sound/usb/pcm.c
> > @@ -806,17 +806,18 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
> >  	if (ret < 0)
> >  		goto unlock;
> >
> > -	iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
> > -	alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
> > -	ret = snd_usb_init_sample_rate(subs->stream->chip,
> > -				       subs->cur_audiofmt->iface,
> > -				       alts,
> > -				       subs->cur_audiofmt,
> > -				       subs->cur_rate);
> > -	if (ret < 0)
> > -		goto unlock;
> > -
> >  	if (subs->need_setup_ep) {
> > +
> > +		iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
> > +		alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
> > +		ret = snd_usb_init_sample_rate(subs->stream->chip,
> > +					       subs->cur_audiofmt->iface,
> > +					       alts,
> > +					       subs->cur_audiofmt,
> > +					       subs->cur_rate);
> > +		if (ret < 0)
> > +			goto unlock;
> > +
> >  		ret = configure_endpoint(subs);
> >  		if (ret < 0)
> >  			goto unlock;
> > --
> > 2.9.3