[Gta04-owner] Beta Tester's Report on qtmoko v40

NeilBrown neilb at suse.de
Tue Feb 28 00:34:32 CET 2012


On Mon, 27 Feb 2012 23:06:47 +0000 Neil Jerram <neil at ossau.homelinux.net>
wrote:

> Sven Dyroff <S.Dyroff at phytec.de> writes:
> 
> > Handling the touch
> > I don't think that I'll get familiar with that behaviour. For me it's just
> > nasty. Please give me at least a hint where I can play with what values and
> > I'll try to squeeze out a more comfortable touch reaction.
> 
> I think you said before that it was too jittery - is that correct?  I
> think I'm sometimes seeing the same problem.
> 
> I don't know what the solution is, or even how to investigate further,
> but:
> 
> - I think I remember a mailing list thread about dejittering support
>   having been removed from the kernel recently (approx in the last year
>   or so), and hence needing to be added to tslib instead.  Or perhaps
>   vice versa?
> 
> - When googling for this, I came across tsc2007_platform_data, and its
>   max_rt, poll_delay and poll_period fields that were recently added by
>   Thierry Reding.  I wonder if these fields might help us?
> 
>   For GTA04 the tsc2007_platform_data struct initialisation (in
>   arch/arm/mach-omap2/board-omap3gta04.c) doesn't set these fields, so I
>   presume they're all implicitly 0.

Correct - which means the defaults are used.

max_rt is an upper-bound for the pressure.  If it senses a higher pressue it
will ignore it.  I wonder why you would do that?  Maybe a high pressue number
is considerred to be an error?
It defaults to MAX_12BIT which means no pressures are ignored.

poll_delay is never used.

poll_period is a number of msec (defaults to '1' but is rounded up to
jiffies, so probably about 5).  It represents how often the current stylus
location is polled.  I doubt increasing that would help much.

> 
> I wondered about experimenting with those fields, but it would be a
> major pain to have to rebuild and reinstall the kernel for every set of
> values to try.
> 
> Any other thoughts on dejittering?

tslib has dejitter code.  See "man 5 tslib.conf".  That is where I would look
to try to improve touchscreen response.

NeilBrown

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