[alsa-devel] [RFC PATCH 5/7] ALSA: hda/hdmi - implement mst_no_extra_pcms flag

[Kai Vehmanen]

Hi Takashi,

On Thu, 29 Aug 2019, Takashi Iwai wrote:

> On Thu, 29 Aug 2019 15:53:46 +0200,
> Kai Vehmanen wrote:
> >  static int generic_hdmi_build_pcms(struct hda_codec *codec)
> >  {
[...]
> > +	if (codec->mst_no_extra_pcms)
> > +		pcm_num = spec->num_nids;
> > +	else
> > +		pcm_num = spec->num_nids + spec->dev_num - 1;
>
> Instead of changing this, we can simply take dev_num=1 like below.
[...]
> -	if (is_haswell_plus(codec)) {
> +	if (codec->mst_no_extra_pcms) {
> +		/* for SOF/SST, no backup PCM streams can be assigned */
> +		dev_num = 1; 
> +		spec->dev_num = 1;
> +	} else if (is_haswell_plus(codec)) {

hmm, I think we need to keep dev_num as 3, to create the MST per_pin 
structs for each port. I.e. we still have the virtual pins, although we 
limit PCM count to 3. Unless we do this, at least jack detection is broken 
in DP-MST mode.

One option would be to set
   dev_num = 3;
   spec->dev_num = 1;

... spec->dev_num is not really used elsewhere than 
generic_hdmi_build_pcms(), so this works.

But, but, this seems quite confusing. So ok if I keep in original form and 
have separate logic in generic_hdmi_build_pcms()?

Br, Kai