[alsa-devel] [PATCH]ASoc:ZOOM2:Add support for DSP rendering.

[Mark Brown]

On Mon, Nov 09, 2009 at 11:22:47AM -0600, Wang, Jane wrote:

Please fix your MUA to word wrap your mails; it makes them very much
more legible and easy to reply to.

> The scenario is data is going between DSP<->McBSP<->TWL4030. DSP
> configures and controls McBSP ports. Since DSP does not have control
> over TWl4030 codec, the role of ALSA here is providing mixer controls
> for user space application to configure codec to prepare for DSP
> rendering.

So in this setup the DSP is essentially a separate device on the audio
bus; it's very much similar to things like the bluetooth chipset you can
see in the OpenMoko devices and ought to be presented in a similar way
as a separate DAI.

> TWL4030 driver does not provide explicit controls over DAC/ADC, mic
> bias, APLL, headset pop-noise attenuation etc, and we need these to make
> playback/capture happen. I can think of two ways to handle this, one is
> add controls in codec to explicitly control these widgets, or using DAPM
> stream events as a single control to power up/down the path. And I feel
> the second solution is cleaner...

Representing the DSP DAI to ASoC is what's needed here, check out the
OpenMoko code for an example of solving a similar problem.