[alsa-devel] DP1.2 MST audio support discussion

[Yang, Libin]

Please check the attachment for details.

Regards,
Libin


> -----Original Message-----
> From: Yang, Libin
> Sent: Tuesday, October 13, 2015 2:26 PM
> To: 'Takashi Iwai'; Lin, Mengdong; tanuk at iki.fi; David Henningsson;
> Girdwood, Liam R
> Cc: alsa-devel at alsa-project.org; airlied at linux.ie
> Subject: DP1.2 MST audio support discussion
> 
> Hi Takashi and all,
> 
> We are planning to enable DP1.2 MST (Multi-Stream Transport)
> audio.
> 
> Based on the previous discussion, we will extend the
> struct hdmi_spec_per_pin to support MST audio device entry.
> So the struct hdmi_spec_per_pin can be a real pin or a device
> entry in the pin.  The idea is to add a member dev_idx in the
> struct hdmi_spec_per_pin. Dev_idx, together with pin_nid,
> can represent a device entry.
> 
> 1. Dynamic PCM assignment
> We will use dynamic PCM assignment for MST audio. This
> means we will create a fixed number of PCMs (the number
> is the same convertor number). All the created PCMs will not
> be assigned to any pin (device entry). When there is a monitor
> connected, an available PCM will be assigned to the pin. And
> it will be de-assigned when the monitor is disconnected.
> Userspace can fetch the HW param when monitor connection
> status is changed.
> 
> I'm not sure how to notify the userspace, such as notifying
> pulseaudio the PCM is assigned or de-assigned. Any ideas?
> 
> 2. Compatibility.
> We will patch patch_hdmi.c to support the MST audio.
> Will we use mst audio driver to support the old mode
> or we use a flag, when HW doesn't support MST audio,
> we will use the old code? Suppose MST audio driver should
> be able support both MST audio and non-MST audio.
> 
> 
> Regards,
> Libin
> 

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