Re: [PATCH 1/5] tsc2007: Debounce pressure measurement.

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, May 17, 2011 at 08:27:16AM +0200, Thierry Reding wrote:
> [Cc'ing Kwangwoo via the alternate email address]
> 
> * Dmitry Torokhov wrote:
> > On Mon, May 16, 2011 at 10:32:59AM +0200, Thierry Reding wrote:
> > > When the controller signals a pen-down event via the platform-specific
> > > GPIO, while the sample values indicate an invalid measurement, the
> > > measurement needs to be repeated.
> > > 
> > 
> > Would not we be interrupted again and take another sample then?
> 
> Not necessarily. The problem is that if the pendown GPIO reports pendown, it
> doesn't necessarily mean that the pressure measurement will be valid. This is
> especially true if max_rt is configurable (as introduced by one of the
> follow-up patchs).
> 
> What happens is that we are interrupted, check the GPIO to see that the pen
> is indeed down and then read the values and compute the pressure to see that
> it is invalid and we stop sampling. The TSC2007's nPEN_IRQ line never goes
> high again after that because the pen is still down (according to the GPIO).
> 
> The comment in the old code of the (rt > max_rt) even says "[...] repeat at
> least once more the measurement", which the old code actually doesn't.
> 

I see. I am concerned with resubmitting work over and over when we do
not have ts->get_pendown_state method.

-- 
Dmitry