On Thu, Feb 11, 2010 at 03:03:17PM -0800, Johnson, Charles F wrote:

I'm trying to understand the level of jack detection implemented in ALSA. I admit some amount of ignorance here - is this documented somewhere that I haven't been able to find yet ??

I'm not sure what exactly you're looking for here but the API used for jack reporting is documented here:

http://www.kernel.org/pub/linux/kernel/people/tiwai/docs/alsa-driver-api/ch0...

The jack will appear as an input device. If you're working on an embedded system then ASoC has a wrapper around this which hooks in to DAPM and makes it easier to combine multiple jack detection methods into a single jack (eg, for microphone plus headphone detection on a headset jack).