Re: [PATCH 2/3] Input: of_touchscreen - fix setting max values on X/Y axis

[Roger Quadros]

Dmitry,

On 07/07/15 19:25, Dmitry Torokhov wrote:
> Hi Roger,
>
> On Tue, Jul 07, 2015 at 12:37:31PM +0300, Roger Quadros wrote:
> > Hi Dmitry,
> >
> > On 07/07/15 03:27, Dmitry Torokhov wrote:
> > > The binding specification says that "touchscreen-size-x" and "-y" specify
> > > horizontal and vertical resolution of the touchscreen and therefore maximum
> > > absolute coordinates should be reduced by 1 since we are starting with 0.
> > >
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > > ---
> > >   drivers/input/touchscreen/of_touchscreen.c | 10 ++++++----
> > >   1 file changed, 6 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/input/touchscreen/of_touchscreen.c b/drivers/input/touchscreen/of_touchscreen.c
> > > index 759cf4b..50bc0f2 100644
> > > --- a/drivers/input/touchscreen/of_touchscreen.c
> > > +++ b/drivers/input/touchscreen/of_touchscreen.c
> > > @@ -71,23 +71,25 @@ void touchscreen_parse_of_params(struct input_dev *dev, bool multitouch)
> > >
> > >   	axis = multitouch ? ABS_MT_POSITION_X : ABS_X;
> > >   	data_present = touchscreen_get_prop_u32(np, "touchscreen-size-x",
> > > -						input_abs_get_max(dev, axis),
> > > +						input_abs_get_max(dev,
> > > +								  axis) + 1,
> >
> > Why do we need to pass default_value to touchscreen_get_prop_u32()?
> > If the property doesn't exist we are not updating the parameter
> > anyway right?
>
> The binding can specify max, fuzz, both, or neither. If only one is
> specified we do not want to "undo" whatever the driver did (for example

why not? At least that is not what touchscreen_parse_properties() does.
It will update the touchscreen params if any one of the DT property is 
present.

> tsc2005 sets up the default maximums before trying to parse OF), so we
> fetch the current value and pass it on as default one.

This is what would happen in tsc2005 case

-driver first sets ABS_X_max to 0xfff and ABS_Y_max to 0xfff.
-calls touchscreen_parse_properties()
-which calls touchscreen_get_prop_u32(dev, "touchscreen-size-x", 
0xfff+1, &maximum)
-if DT properties are missing, touchscreen_get_prop_u32() changes
ABS_X_max to 0x1000 and returns false.
- as data_present is false we don't do a -1 and so we have ABS_X_max 
changed to 0x1000.

This doesn't look right.

So IMO default_value parameter can be removed from 
touchscreen_get_prop_u32() to make things simpler.

If the property doesn't exist it will not change *value and return false.

cheers,
-roger
-
> > >   						&maximum) |
> > >   		       touchscreen_get_prop_u32(np, "touchscreen-fuzz-x",
> > >   						input_abs_get_fuzz(dev, axis),
> > >   						&fuzz);
> > >   	if (data_present)
> > > -		touchscreen_set_params(dev, axis, maximum, fuzz);
> > > +		touchscreen_set_params(dev, axis, maximum - 1, fuzz);
> > >
> > >   	axis = multitouch ? ABS_MT_POSITION_Y : ABS_Y;
> > >   	data_present = touchscreen_get_prop_u32(np, "touchscreen-size-y",
> > > -						input_abs_get_max(dev, axis),
> > > +						input_abs_get_max(dev,
> > > +								  axis) + 1,
> > >   						&maximum) |
> > >   		       touchscreen_get_prop_u32(np, "touchscreen-fuzz-y",
> > >   						input_abs_get_fuzz(dev, axis),
> > >   						&fuzz);
> > >   	if (data_present)
> > > -		touchscreen_set_params(dev, axis, maximum, fuzz);
> > > +		touchscreen_set_params(dev, axis, maximum - 1, fuzz);
> > >
> > >   	axis = multitouch ? ABS_MT_PRESSURE : ABS_PRESSURE;
> > >   	data_present = touchscreen_get_prop_u32(np, "touchscreen-max-pressure",
>
> Thanks.
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