[alsa-devel] [PATCH 3/4] ALSA: hda - display audio call ncts callback

[Yang, Libin]

Hi Raymond,

>
> > >     }
> > >
> > > +   if (is_haswell_plus(codec)) {
> > > +           if (acomp && acomp->ops && acomp->ops->set_ncts)
> > > +                   acomp->ops->set_ncts(acomp->dev, per_pin-
> > >pin_nid - 4,
> >
> > Please describe more how "pin_nid - 4" is supposed to work.  Also...
>
> OK, I see.
>
> >
> > > +                           0, runtime->rate);
> >
> > ... this implies that no MST support included?
>
> We will support MST later. Currently I just add the
> interface to support MST, but not implementing it.
Refer to DCN HDA040-A
Multi-stream over Single Display Port
Can the driver use subdevices for those display port support multi streaming ?

[Libin] What do you mean subdevice here, 
using a struct device to represent a dev_entry or an int type?

The specification allow up to 64 device entries
This mean the number of subdevices is equal to the device list length
More than one audio output /converters can be connected to the multi stream displayport pin widget but different device entry while only one audio output can be dynamically allocated  to other HDMI pin widget

[Libin] Yes, Pin widget can have multiple device entry and connecting different converters. The audio output will be based on device entry.

7.3.3.42 Device Select
For Digital Display Pin Widget that is multi stream capable, the Device Select control determines which Device Entry is currently selected and accessible by the Pin Widget verbs which are controlling the sink device operations.  This control verb is only required if it is a Digital Display Pin Widget and multi stream capable.
The index is in relation to the Device List associated with the widget.  The index is a zero-based offset into the Device List.  Once the Device Entry is selected by the Set index, all subsequent Pin Widget verbs controlling the sink device operations will be directed to the selected Device Entry, until the Device Select verb get updated with a new value.  
Device Entry: Indicate the index of Device Entry (0 63) which the UR bit of is generated for a multi stream capable Digital Display Pin Widget.  Not valid for non Digital Display Pin Widget or Digital Display Pin Widget that is not multi stream capable
Device List Length is a 0 based integer value indicating the number of sink device that a multi stream capable Digital Display Pin Widget can support.  If Device List Length is value is 0, there is only one sink device connection possible indicating the Pin Widget is not multi stream capable, and there is no Device Select control (see Section 7.3.3.42).  If the Device List Length value is 1 – 63, it indicates the Pin Widget is multi stream capable, and 2 – 64 Device Entries are supported in the Pin Widget. 
>

Regards,
Libin