linux-kernel - Re: [PATCH v1 2/3] sound: usb: Calling vendor's call-back function within usb audio operation.

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Date:   Fri, 25 Mar 2022 16:13:57 +0900
From:   Oh Eomji <eomji.oh@...sung.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        open list <linux-kernel@...r.kernel.org>,
        alsa-devel@...a-project.org, Leon Romanovsky <leon@...nel.org>,
        Pavel Skripkin <paskripkin@...il.com>
Subject: Re: [PATCH v1 2/3] sound: usb: Calling vendor's call-back function
 within usb audio operation.

On Thu, Mar 24, 2022 at 09:34:22AM +0100, Greg Kroah-Hartman wrote:
> On Thu, Mar 24, 2022 at 05:10:43PM +0900, Oh Eomji wrote:
> > When a new interface is connected or removed, the call-back functions
> > are called to transmit a command to the hardware.
> > 
> > Signed-off-by: Oh Eomji <eomji.oh@...sung.com>
> > ---
> >  sound/usb/pcm.c    | 37 +++++++++++++++++++++++++++++++++++++
> >  sound/usb/stream.c |  2 ++
> >  2 files changed, 39 insertions(+)
> > 
> > diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> > index cec6e91a..4bae4ba 100644
> > --- a/sound/usb/pcm.c
> > +++ b/sound/usb/pcm.c
> > @@ -144,6 +144,8 @@ find_format(struct list_head *fmt_list_head, snd_pcm_format_t format,
> >  			found = fp;
> >  			cur_attr = attr;
> >  		}
> > +
> > +		snd_vendor_set_pcm_binterval(fp, found, &cur_attr, &attr);
> >  	}
> >  	return found;
> >  }
> > @@ -434,6 +436,7 @@ static int configure_endpoints(struct snd_usb_audio *chip,
> >  			       struct snd_usb_substream *subs)
> >  {
> >  	int err;
> > +	struct usb_interface *iface;
> >  
> >  	if (subs->data_endpoint->need_setup) {
> >  		/* stop any running stream beforehand */
> > @@ -442,6 +445,13 @@ static int configure_endpoints(struct snd_usb_audio *chip,
> >  		err = snd_usb_endpoint_configure(chip, subs->data_endpoint);
> >  		if (err < 0)
> >  			return err;
> > +
> > +		iface = usb_ifnum_to_if(chip->dev, subs->data_endpoint->iface);
> > +		err = snd_vendor_set_pcm_intf(iface, subs->data_endpoint->iface,
> > +				subs->data_endpoint->altsetting, subs->direction);
> > +		if (err < 0)
> > +			return err;
> > +
> >  		snd_usb_set_format_quirk(subs, subs->cur_audiofmt);
> >  	}
> >  
> > @@ -616,8 +626,18 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
> >  	struct snd_pcm_runtime *runtime = substream->runtime;
> >  	struct snd_usb_substream *subs = runtime->private_data;
> >  	struct snd_usb_audio *chip = subs->stream->chip;
> > +	struct snd_usb_endpoint *ep = subs->data_endpoint;
> >  	int ret;
> >  
> > +	ret = snd_vendor_set_pcm_buf(subs->dev, subs->cur_audiofmt->iface);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (!subs->cur_audiofmt) {
> > +		dev_err(&subs->dev->dev, "no format is specified\n");
> > +		return -ENXIO;
> > +	}
> > +
> >  	ret = snd_usb_lock_shutdown(chip);
> >  	if (ret < 0)
> >  		return ret;
> > @@ -630,6 +650,13 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
> >  	if (ret < 0)
> >  		goto unlock;
> >  
> > +	if (snd_vendor_get_ops()) {
> > +		ret = snd_vendor_set_rate(ep->cur_audiofmt->iface,
> > +				ep->cur_rate, ep->cur_audiofmt->altsetting);
> > +		if (!ret)
> > +			goto unlock;
> > +	}
> > +
> >  	/* reset the pointer */
> >  	subs->buffer_bytes = frames_to_bytes(runtime, runtime->buffer_size);
> >  	subs->inflight_bytes = 0;
> > @@ -1104,6 +1131,11 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream)
> >  	struct snd_usb_substream *subs = &as->substream[direction];
> >  	int ret;
> >  
> > +	ret = snd_vendor_set_pcm_connection(subs->dev, SOUND_PCM_OPEN,
> > +					    direction);
> > +	if (ret)
> > +		return ret;
> > +
> >  	runtime->hw = snd_usb_hardware;
> >  	/* need an explicit sync to catch applptr update in low-latency mode */
> >  	if (direction == SNDRV_PCM_STREAM_PLAYBACK &&
> > @@ -1137,6 +1169,11 @@ static int snd_usb_pcm_close(struct snd_pcm_substream *substream)
> >  	struct snd_usb_substream *subs = &as->substream[direction];
> >  	int ret;
> >  
> > +	ret = snd_vendor_set_pcm_connection(subs->dev, SOUND_PCM_CLOSE,
> > +					    direction);
> > +	if (ret)
> > +		return ret;
> > +
> >  	snd_media_stop_pipeline(subs);
> >  
> >  	if (!snd_usb_lock_shutdown(subs->stream->chip)) {
> > diff --git a/sound/usb/stream.c b/sound/usb/stream.c
> > index ceb93d7..26ca696 100644
> > --- a/sound/usb/stream.c
> > +++ b/sound/usb/stream.c
> > @@ -1227,6 +1227,8 @@ static int __snd_usb_parse_audio_interface(struct snd_usb_audio *chip,
> >  		snd_usb_init_pitch(chip, fp);
> >  		snd_usb_init_sample_rate(chip, fp, fp->rate_max);
> >  		usb_set_interface(chip->dev, iface_no, altno);
> > +		if (protocol > UAC_VERSION_1)
> 
> Why the protocol check?  That's not documented in your changelog
> anywhere :(
> 
>
Hi,

In kernel 5.10, set_interface is performed when the protocol is more
than UAC_VERSION_1 in the snd_usb_init_sample_rate function.
There was an issue here, so there is a history of adding to perform
snd_vendor_set_interface when the protocol is more than UAC_VERSION_1.
But I don't think I need this in kerenel 5.15, so I'll delete it.

Thanks,
Eomji Oh