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

[Takashi Iwai <tiwai@suse.de>]

On Wed, 16 Mar 2016 08:48:58 +0100,
Yang, Libin wrote:
> 
> Hi Takashi,
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai@suse.de]
> > Sent: Wednesday, March 16, 2016 3:35 PM
> > To: libin.yang@linux.intel.com
> > Cc: alsa-devel@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@linux.intel.com wrote:
> > >
> > > From: Libin Yang <libin.yang@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@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.

But the pin widget is the terminal.  So, if you have a device index to
choose a device there, the widget connection list itself doesn't
change.  Or am I missing anything?


Takashi
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