[alsa-devel] [PATCH] ALSA: hda - codec add DP MST support for connection list

[Yang, Libin]

Hi Takashi,

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Wednesday, March 16, 2016 3:35 PM
> To: libin.yang at linux.intel.com
> Cc: alsa-devel at alsa-project.org; Yang, Libin; Lin, Mengdong
> Subject: Re: [alsa-devel] [PATCH] ALSA: hda - codec add DP MST support
> for connection list
> 
> On Wed, 16 Mar 2016 02:47:31 +0100,
> libin.yang at linux.intel.com wrote:
> >
> > From: Libin Yang <libin.yang at linux.intel.com>
> >
> > This patches adds the support of connection list for DP MST.
> > With this, hdmi driver in DP MST mode can easily reuse
> > the connection list mechanism.
> >
> > Signed-off-by: Libin Yang <libin.yang at linux.intel.com>
> 
> The merge window was already opened, so it's too late for this kind of
> change for 4.6, in anyway.

That's OK. We can wait for later version. What do you think put this patch
and my later patches for MST in the topic branch, such as hdmi-jack brach
like before. Later patches for MST needs gfx driver support and our
gfx driver is not ready for it.

> 
> But, the fundamental question: why do we need to manage the cached
> list of the widget connection with a device index?  In other words, if
> you have a different device index, does the widget connection itself
> also change?

Based on my test, it should be the same. But from the spec, it says:

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. These Pin Widget verbs include:
  Connection Select 
  Get Connection List Entry
  Amplifier Gain/Mute
  Power State
  Pin Widget Control
  ELD Data
  DIP-Size
  DIP-Index
  DIP-Data
  DIP-XmitCtrl
  Content Protection Control
  ASP Channel Mapping

So my understand is this may be changed.

Regards,
Libin

> 
> 
> Takashi