Hi,
On 11-10-18 02:52, Dmitry Torokhov wrote:
Hi Hans,
Sorry, now I was being slow as well.
No problem.
On Thu, Sep 20, 2018 at 07:31:43PM +0200, Hans de Goede wrote:
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.
Right, except that my concern is that people do not read documentation,
and therefore will not realize that touchscreen-size-x is not the "true"
what I called it, or what you call usable range, but rather maximum
coordinate (-1). IOW I am concerned that if we have a device with
640x480 screen for example, and touch controller reporting coordinates
with offset of 20, someone will specify:
touchscreen-min-x = 20
touchscreen-size-x = 640 (because that's their screen size)
and will not notice for some reason and later quirk it in their
software.
Ah I see.
So I was asking if we should accommodate this, and actually set up max
on axis as "touchscreen-min-x + touchscreen-size-x - 1". It will still
be compatible with current bindings (having effectively min of 0), but
to me better reflects the name of the parameter - size of the screen.
Please let me know if this makes any sense to you.
I understand what you want now and why you want it.
But I'm not sure I agree with you. Some pre-cursor to this patch series
actually had something like touchscreen-offset-x (or some-such I don't
remember) which actually subtracted the specified value from the coordinates
reported to userspace (clamping to 0).
In that setup I think setting:
touchscreen-size-x = (maximum x coordinate reported + 1) -
(minimum x coordinate reported.
Makes sense, but since now we are not doing that and just copying the
values over to input_absinfo.minimum/maximum I think a 1:1 mapping
(with the - 1 adjustment for size) makes more sense.
The way I'm currently using this is with touchscreens where we cannot
read this info from the hardware, so I repeatedly move my finger over
each edge noting down the min / max value for e.g. the left/right
edge and then directly putting these into the properties.
IMHO not having to do some math here to calculate the right value
for touchscreen-size-x shows that treating touchscreen-size-x as
(touchscreen-max-x + 1) is the right thing to do.
I'm actually worried that if we follow your suggestion people will
indeed not read the docs and thus not do the math. I think they will
just copy over the min / max readings and we and up with an
input_absinfo.maximum value which is input_absinfo.minimum
units too big.
Regards,
Hans
