[alsa-devel] [PATCH v2] ASoC: hdac_hdmi: Program pin-port-mux during jack report event

[Takashi Iwai]

On Wed, 11 Jul 2018 12:56:03 +0200,
Sriram Periyasamy wrote:
> 
> On Wed, Jul 11, 2018 at 12:03:14PM +0200, Takashi Iwai wrote:
> > On Wed, 11 Jul 2018 11:25:46 +0200,
> > Sriram Periyasamy wrote:
> > > 
> > > On Wed, Jul 11, 2018 at 08:45:05AM +0200, Takashi Iwai wrote:
> > > > On Wed, 11 Jul 2018 08:30:43 +0200,
> > > > Sriram Periyasamy wrote:
> > > > > +		if (port->pin->conn_index > 0)
> > > > > +			snd_hdac_codec_write(&edev->hdev, port->pin->nid,
> > > > > +						0, AC_VERB_SET_CONNECT_SEL,
> > > > > +						port->pin->conn_index - 1);
> > > > 
> > > > And, here checks conn_index > 0 while...
> > > > 
> > > > > @@ -903,6 +931,9 @@ static int hdac_hdmi_set_pin_port_mux(struct snd_kcontrol *kcontrol,
> > > > >  		}
> > > > >  	}
> > > > >  
> > > > > +	if (ucontrol->value.enumerated.item[0] > 0)
> > > > > +		port->pin->conn_index =	ucontrol->value.enumerated.item[0];
> > > > 
> > > > ... conn_index is set only non-zero here.
> > > > 
> > > > That is, once after a non-zero is passed, conn_index can't any longer
> > > > back to zero.  I guess it's not intentional?
> > > > 
> > > 
> > > No, it is intentional. For example, two ports are connected to the
> > > display and user land set mux only for one port. Hence other port's
> > > conn_index is set to default 0. When jack report happens for that port,
> > > we would be writing invalid connection select index which will lead to
> > > undefined hardware behaviour as per the HDA spec.
> > > 
> > > Though it is userland's mistake, it is better to take care in the driver.
> > 
> > Then wouldn't it be better to remember the last set value in
> > hdac_hdmi_pin_mux_widget_event()?  The purpose of the patch is to
> > restore the previous state.
> > 
> 
> Since hdac_hdmi_pin_mux_widget_event() invoked only for current playback
> pin-port-mux path, we wouldn't restore other port's indices. So
> hdac_hdmi_jack_report() chosen which will restore other ports also in
> all use cases.

Hm, it sounds like really more black magic behind the scene.
Please give more descriptions to the patch and/or codes.


Takashi