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

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Date:   Thu, 1 Dec 2016 16:07:07 +0900
From:   Jiada Wang <jiada_wang@...tor.com>
To:     Takashi Iwai <tiwai@...e.de>
CC:     <perex@...ex.cz>, <alsa-devel@...a-project.org>,
        <apape@...adit-jv.com>, <Mark_Craske@...tor.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3 v2] ALSA: usb-audio: avoid setting of sample rate
 multiple times on bus

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@...adit-jv.com>
>>
>> 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@...adit-jv.com>
>> Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
>
> 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
>>
>>