[PATCH] ALSA: hda/hdmi: let new platforms assign the pcm slot dynamically

[Kai Vehmanen]

Hi,

On Tue, 23 Feb 2021, Takashi Iwai wrote:

> On Tue, 23 Feb 2021 17:25:23 +0100, Jaroslav Kysela wrote:
> > A dumb question: Does TGL really support up to 11 separate displays or it's
> > just to handle 11 connections and the number of maximal simultanenous
> > connected displays is lower? In the later case, the dynamic allocation makes
> 
> That's the latter.  And, the fixed assignment was merely for
> compatibility with legacy usage, and supposed to be 3 fixed ones or
> so.  Extending to that high number wasn't intended when the mechanism
> was introduced.  We should have noticed it at ICL support (which has
> up to 6 devices).

yes, exactly. The pins relate to physical ports. There are more pins now 
to cater for various DP-over-USB-C topologies (versus just native HDMI and 
DP ports). Most product have less physical ports connected, but on the HDA 
interface all pins are exposed. Each pin does provide functionality to 
query whether a display is connected to it, and whether the connected 
display has audio capability.

The maximum number of concurrent displays is described as converters.
On TGL this is 4.

With SOF, we didn't have legacy userspace, so the HDMI/DP PCMs are already 
exposed differently and only a small number (3 or 4) of PCMs are created 
depending on hardware generation. Now the question is how we move 
snd-hda-intel to similar model with minimal distraction to existing 
user-space.

Br, Kai