Re: [RFC PATCH 2/2] bttv: fix audio mute on device close for the radio device node

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Am 10.03.2013 12:59, schrieb Hans Verkuil:
> On Sun March 10 2013 12:40:35 Frank Schäfer wrote:
>> Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
>> ---
>>  drivers/media/pci/bt8xx/bttv-driver.c |    5 ++++-
>>  1 Datei geändert, 4 Zeilen hinzugefügt(+), 1 Zeile entfernt(-)
>>
>> diff --git a/drivers/media/pci/bt8xx/bttv-driver.c b/drivers/media/pci/bt8xx/bttv-driver.c
>> index 2c09bc5..74977f7 100644
>> --- a/drivers/media/pci/bt8xx/bttv-driver.c
>> +++ b/drivers/media/pci/bt8xx/bttv-driver.c
>> @@ -3227,6 +3227,7 @@ static int radio_open(struct file *file)
>>  	v4l2_fh_init(&fh->fh, vdev);
>>  
>>  	btv->radio_user++;
>> +	audio_mute(btv, btv->mute);
>>  
>>  	v4l2_fh_add(&fh->fh);
>>  
>> @@ -3248,8 +3249,10 @@ static int radio_release(struct file *file)
>>  
>>  	bttv_call_all(btv, core, ioctl, SAA6588_CMD_CLOSE, &cmd);
>>  
>> -	if (btv->radio_user == 0)
>> +	if (btv->radio_user == 0) {
>>  		btv->has_radio_tuner = 0;
>> +		audio_mute(btv, 1);
>> +	}
>>  	return 0;
>>  }
>>  
>>
> Sorry, but this isn't right.
>
> You should be able to just set the radio to a frequency and then exit. Since
> most cards have an audio out that loops to an audio input you don't want to
> have to keep the radio device open.

Ok, so I will drop this patch.

AFAICS the above said also applies to the video device part, so it's
still not clear to me why both devices should be handled differently.
Anyway, I will regard it as a kind of "tradition".

>
> Audio should be muted when the module is unloaded, though.
>
> The relationship between TV and radio tuners was discussed last year. The
> following proposal was accepted:
>
> ------- start -----------
> How to handle tuner ownership if both a video and radio node share the same
> tuner?
>
> Calling S_FREQ, S_TUNER, S_MODULATOR or S_HW_FREQ_SEEK will make the filehandle
> the owner if possible. EBUSY is returned if someone else owns the tuner and you
> would need to switch the tuner mode.
>
> Ditto for ioctls that expect a valid tuner configuration like QUERYSTD. This is
> likely to be driver dependent, though. Just opening a device node should not
> switch ownership.
>
> G_FREQUENCY: should just return the last set frequency for radio or TV: requires
> that that is remembered when switching ownership. This is what happens today, so
> G_FREQUENCY does not have to switch ownership.
>
> G_TUNER: the rxsubchans, signal and afc fields all require ownership of the tuner.
> So in principle you would want to switch ownership when G_TUNER is called. On the
> other hand, that would mean that calling v4l2-ctl --all -d /dev/radio0 would change
> tuner ownership to radio for /dev/video0. That's rather unexpected.
>
> So just set rxsubchans, signal and afc to 0 if the device node doesn't own the tuner.
>
> Closing a device node should not switch ownership. E.g. if nobody has a radio device
> open, should the tuner switch back to TV mode automatically? The answer is that it
> shouldn't.
>
> How about hybrid tuners? The code to handle tuner ownership should be shared between
> DVB and V4L2.
> ----------- end --------------
>
> All very nice, but nobody had the chance to actually work on this.
>
> But this is how it should work.

Interesting, thanks !

Regards,
Frank

>
> Regards,
>
> 	Hans