[alsa-devel] [DAPM question] DAPM support for single input multiple outputs

[Lars-Peter Clausen]

On 03/09/2015 09:38 AM, Qiao Zhou wrote:
> Hi Mark,
>
> I have one question and need your suggestion. Thanks in advance.
>
> In our DSP, one stream path is like this: There is one bit controlling
> whether a signal A goes to A_out or B_out. That's the reverse case of
> DAPM_MUX(multiple inputs, single output).
>
> One way is to use two switches but it seems not good since two switches
> control the same bit. It's strange. Do you have any opinion about such
> requirement support?

There is currently no support for a demux. But it shouldn't be too hard to 
add one in the DAPM core, if you want to take a try at it.

A demux would behave very similar to a mux, except that you'd reverse 
sources and sinks. The only thing that is a bit tricky is that we only have 
one control element per path and currently it always belongs to the sink. 
For a demux it needs to be long to the source. This means you can't have a 
mixer directly connected to the same path as a demux and the core needs to 
make sure that that doesn't happen.

- Lars