[alsa-devel] [PATCH 2/2] ASoC: twl4030 - Add VDL path support

[Mark Brown]

On Tue, Mar 24, 2009 at 09:59:31PM +0900, Joonyoung Shim wrote:
> Adds DAPMs for VDL(voice down link) path.
> To support VDL path, we have to change DAPM of outputs(Earpiece,
> PreDrive Left/Right, Headset Left/Right, Carkit Left/Right) from mux to
> mixer, also codec mode from option1 to option2.

In this specific case where there is no DAI interfacing with the voice
DAC you could just not tell DAPM it's a DAC - it doesn't buy anything
since the only thing that DACs do at the minute is stream 

Alternatively, if this is for something like playback of an audio stream
take a look at how the Neo1973 driver represents the audio downlink from
the bluetooth chipset.  A dummy audio interface is provided to user
space which user space can set up as normal through ALSA, just skipping
actually transferring any data.  This is hacky but has the advantage of
keeping the power management.

There's a sample user space application driving this here:

	http://opensource.wolfsonmicro.com/~gg/bluetooth-pcm/bluetooth_pcm.c