Hi,
I completely missed this mail earlier, sorry.
Thank you Benjamin for pointing this out to me.
On 03-08-18 02:31, Dmitry Torokhov wrote:
Hi Hans,
On Tue, Jul 31, 2018 at 01:19:57PM +0200, Hans de Goede wrote:
Some touchscreens, depending on the firmware and/or the digitizer report
coordinates which never reach 0 along one or both of their axis.
This has been seen for example on the Silead touchscreens on a Onda V891w
and a Point of View mobii TAB-P800w(v2.0).
This commits documents 2 new touchscreen properties for communicating
the minimum reported values to the OS: touchscreen-min-x and -min-y.
This commit also drop the (in pixels) comment from the documentation
of the touchscreen-size-x and touchscreen-size-y properties. This comment
suggests that there is a relation between the range of reported
coordinates and the display resolution, which is only true for some
devices. The (in pixels) comment is replaced with "(maximum x coordinate
reported + 1)" to mirror the language describing the new touchscreen-min-x
and -min-y properties.
I am concerned that people will not read the documentation carefully and
will treat it as true size, since it is what in the name. Maybe we
should say that it is size of usable area, in device units, and that
maximum reported coordinate is "touchscreen-min-x + touchscreen-size-x -
1"?
Not sure what you mean with "true size" but in the implementation
from this series, the maximum coordinated reported is (touchscreen-size-x - 1)
not (touchscreen-min-x + touchscreen-size-x - 1) as you suggest.
Basically what this series does is set:
input_absinfo.minimum to the new touchscreen-min-x value (or 0 if not specified)
input_absinfo.maximum to touchscreen-size-x - 1 as we've always done.
So the usable range / the range mapping from one screen edge to the other is:
touchscreen-min-x - (touchscreen-size-x - 1)
Which matches with the dt bindings doc after this patch, which
reads after this patch:
- touchscreen-min-x : minimum x coordinate reported (0 if not set)
- touchscreen-min-y : minimum y coordinate reported (0 if not set)
- touchscreen-size-x : horizontal resolution of touchscreen
(maximum x coordinate reported + 1)
- touchscreen-size-y : vertical resolution of touchscreen
(maximum y coordinate reported + 1)
I hope this clarifies things and if you want to change anything let
me know.
Regards,
Hans
