[alsa-devel] Dell USB audio driver workaround

[Kailang]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de] 
> Sent: Thursday, April 07, 2016 5:54 PM
> To: Kailang
> Cc: (alsa-devel at alsa-project.org)
> Subject: Re: Dell USB audio driver workaround
> 
> On Thu, 07 Apr 2016 11:45:10 +0200,
> Kailang wrote:
> > 
> >  
> > 
> > > -----Original Message-----
> > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > Sent: Thursday, April 07, 2016 5:27 PM
> > > To: Kailang
> > > Cc: (alsa-devel at alsa-project.org)
> > > Subject: Re: Dell USB audio driver workaround
> > > 
> > > On Thu, 07 Apr 2016 09:05:52 +0200,
> > > Kailang wrote:
> > > > 
> > > >  
> > > > 
> > > > > -----Original Message-----
> > > > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > > > Sent: Wednesday, April 06, 2016 5:37 PM
> > > > > To: Kailang
> > > > > Cc: (alsa-devel at alsa-project.org)
> > > > > Subject: Re: Dell USB audio driver workaround
> > > > > 
> > > > > On Wed, 06 Apr 2016 11:22:43 +0200, Kailang wrote:
> > > > > > 
> > > > > >  
> > > > > > 
> > > > > > > -----Original Message-----
> > > > > > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > > > > > Sent: Wednesday, April 06, 2016 4:57 PM
> > > > > > > To: Kailang
> > > > > > > Cc: (alsa-devel at alsa-project.org)
> > > > > > > Subject: Re: Dell USB audio driver workaround
> > > > > > > 
> > > > > > > On Wed, 06 Apr 2016 08:29:12 +0200, Kailang wrote:
> > > > > > > > 
> > > > > > > > Hi Takashi,
> > > > > > > > 
> > > > > > > > Dell had USB dock.
> > > > > > > > Maybe firmware issue, the master volume always 
> keep at 0x57.
> > > > > > > > Attach patch will fix it to keep at Max volume.
> > > > > > > > 
> > > > > > > > Could you help us to update it?
> > > > > > > 
> > > > > > > Well, I don't get how this patch works..
> > > > > > > 
> > > > > > > > diff --git a/sound/usb/mixer.c 
> b/sound/usb/mixer.c index 
> > > > > > > > 4f85757..84d9a4e 100644
> > > > > > > > --- a/sound/usb/mixer.c
> > > > > > > > +++ b/sound/usb/mixer.c
> > > > > > > > @@ -846,6 +846,12 @@ static void
> > > volume_control_quirks(struct
> > > > > > > > usb_mixer_elem_info *cval,  {
> > > > > > > >  	struct snd_usb_audio *chip = 
> cval->head.mixer->chip;
> > > > > > > >  	switch (chip->usb_id) {
> > > > > > > > +	case USB_ID(0x0bda, 0x4014): /* Dell 
> workaround */
> > > > > > > > +		if (strstr(kctl->id.name, "Playback
> > > > > Volume") != NULL) {
> > > > > > > > +			cval->min = 0x0000;
> > > > > > > > +			cval->max = 0x0000;
> > > > > > > > +		}
> > > > > > > > +		break;
> > > > > > > 
> > > > > > > So, this means that this value has to be fixed to 0?
> > > > > > > If yes, can't we simply remove this volume instead?
> > > > > > 
> > > > > > Yes, but it need to set Max volume to 0. This is test
> > > on my site.
> > > > > > Because it will rewrite 0x57 value to codec register when
> > > > > driver is loaded.
> > > > > > And keep 0x57 volume value all the time. So, Master volume
> > > > > will lower than windows machine.
> > > > > > This case which driver fail to build the alsa mixer(This is
> > > > > firmware cause it). So, no hardware volume control on this.
> > > > > > If the Max volume value is 0,  system will not set default
> > > > > value 0x57 for first time loading driver.
> > > > > 
> > > > > Which values (min/max) does this FU take and which values
> > > are buggy?
> > > > Max value. 
> > > 
> > > Sorry, my question wasn't clear.  "What" min and max are they?  
> > > min=0 and max=0x57?
> > 
> > Sorry!! Codec reg min =0 and max=0x7f
> > 
> > 
> > > 
> > > And, your patch changes both min and max to be 0.  That is, it 
> > > accepts only 0.  Does it mean that this FU isn't any 
> proper volume 
> > > control?
> > 
> > Ubuntu => pulseaudio will use digital volume to control 
> volume. Codec volume register fixed it to Max.
> >                    
> > Chromebook => CRAS lib also use digital volume to control 
> volume. Codec volume register fixed it to Max.
> 
> Right, it's normal behavior for most of sound systems.  But 
> how writing "0" would make it still working?  Or am I 
> misunderstanding the purpose of your patch?
> 
> Again your patch changes like:
> 
> > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 
> > 4f85757..84d9a4e 100644
> > --- a/sound/usb/mixer.c
> > +++ b/sound/usb/mixer.c
> > @@ -846,6 +846,12 @@ static void volume_control_quirks(struct 
> > usb_mixer_elem_info *cval,  {
> >  	struct snd_usb_audio *chip = cval->head.mixer->chip;
> >  	switch (chip->usb_id) {
> > +	case USB_ID(0x0bda, 0x4014): /* Dell workaround */
> > +		if (strstr(kctl->id.name, "Playback Volume") != NULL) {
> > +			cval->min = 0x0000;
> > +			cval->max = 0x0000;
> > +		}
> > +		break;
> 
> This should "fix" to the value 0, which is the minimum value, right?

Oh! Yes. 
Sorry!  I confuse with min and max value.
It should be 0 for min value.
I had test other method. But it still not pull up codec volume to Max value.

> 
> 
> Takashi
> 
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