On Thu, Jan 10, 2013 at 05:06:11PM +0100, Lars-Peter Clausen wrote:
More specific this will be used by the ADAU1361 driver where the hardware has a mute control for each of the DAC output paths, but we have to make sure that the path is muted whenever the DAC is disabled. So the mute switches needs to be controlled by DAPM so it can disable them before disabling the DAC. On the other hand we still want to be to mute individual paths. This will be accomplished by using virtual switch controls.
This doesn't sound like it does quite what you want - it means you don't actually end up with a mute control, only a power control (which is also going to affect everything else in the path). I'd expect to see something like this implemented by having a control that has a specified value forced in the register while the control is enabled (kind of the opposite of a supply). This is a fairly common need for older parts though it's unusual to see it on a new device.