Re: [PATCH] Input: of_touchscreen / generic bindings - Add support for touchscreen-min-x|y

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 31-05-18 19:25, Rob Herring wrote:
> On Tue, May 29, 2018 at 01:52:38PM +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 commit adds support for touchscreen-min-x and touchscreen-min-y
>> device-properties which can be set to communicate the actual start
>> coordinates (rather then 0,0) to userspace.
>>
>> When set this fixes e.g. not being able to click things in the GNOME3
>> top-bar on the 2 example tablets.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   .../input/touchscreen/touchscreen.txt         |  6 ++--
> 
> Please split bindings to separate patch.

Will do for v2.

>>   drivers/input/touchscreen/of_touchscreen.c    | 36 ++++++++++++++-----
>>   2 files changed, 32 insertions(+), 10 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
>> index 537643e86f61..8aff9551259f 100644
>> --- a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
>> +++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
>> @@ -1,10 +1,12 @@
>>   General Touchscreen Properties:
>>   
>>   Optional properties for Touchscreens:
>> + - touchscreen-min-x		: minimum x coordinate reported (0 if not set)
>> + - touchscreen-min-y		: minimum y coordinate reported (0 if not set)
> 
> Maybe a min-max range would be better if size (in pixels) is also
> needed?

Size in pixels is never needed. The touchscreen-size-x /
touchscreen-size-y have always been the max x/y coordinate reported + 1
and may or may not have anything to do with pixels. I've noticed on
some ARM tablets that the firmware in the touchscreen controller was
programmed to send coordinates in the same range as the display
resolution, but then the manufacturer would turn around, put in
a higher res display and keep the same touchscreen range (or the
otherway around). So it seems that there has been a 1:1 mapping on
some devices, but that has not been true for a long time now.

>>    - touchscreen-size-x		: horizontal resolution of touchscreen
>> -				  (in pixels)
>> +				  (maximum x coordinate reported + 1)
> 
> This is unrelated or at least not explained in the commit msg. I agree
> this probably makes sense as units are often not pixels unless the hw/fw
> is doing some scaling itself.

Right I added this fix to make clear that we are indeed specifying a
min-max range, with the oddity that instead of max we specify max + 1
for historical reasons.

Do you want me to split this out into a separate patch?

Regards,

Hans


> 
>>    - touchscreen-size-y		: vertical resolution of touchscreen
>> -				  (in pixels)
>> +				  (maximum y coordinate reported + 1)
>>    - touchscreen-max-pressure	: maximum reported pressure (arbitrary range
>>   				  dependent on the controller)
>>    - touchscreen-fuzz-x		: horizontal noise value of the absolute input