Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Mark Brown]

On Mon, Jan 09, 2017 at 08:29:53PM +0100, Pali Rohár wrote:
> On Monday 09 January 2017 20:22:01 Mark Brown wrote:

> > point where you need an actual change.  Note that if something holds
> > the microphone bias on (like something using the microphone)
> > separately then that'll take effect so if you really need things to
> > get turned off then that won't work but you probably have trouble
> > anyway in that situation.

> This is needed for cable/jack detection at time when jack is inserted. 
> So before it there cannot be any user of (disconnected) microphone.

That's not going to stop userspace, consider what happens if the headset
gets removed and userspace is slow to stop a recording for example.

> What I need is to enable mic bias, measure ADC of some time period, 
> check status of some GPIOs. Then disable mic bias, measure ADC again and 
> check GPIOs. I in this detection procedure I need to ensure that nobody 
> changes mic bias. So I though that locking the whole procedure could 
> ensure that.

That sounds racy and a bit unusual - what's the actual procedure here?

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