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Date:   Mon, 20 Feb 2017 23:21:37 +0100
From:   Petr Cvek <>
To:     Dmitry Torokhov <>,
        "H. Nikolaus Schaller" <>
Cc:     Pali Rohár <>,
        Sebastian Reichel <>,
        Mark Rutland <>,
        Benoît Cousson <>,
        Tony Lindgren <>,
        Russell King <>,
        Arnd Bergmann <>,
        Michael Welling <>,
        Mika Penttilä <>,
        Javier Martinez Canillas <>,
        Igor Grinberg <>,
        "Andrew F. Davis" <>, Mark Brown <>,
        Jonathan Cameron <>,
        Rob Herring <>,
        Alexander Stein <>,
        Eric Engestrom <>,
        Hans de Goede <>,
        Benjamin Tissoires <>,
        Mauro Carvalho Chehab <>,
        Hans Verkuil <>,
        Nick Dyer <>,
        Siebren Vroegindeweij <>,
        Michel Verlaan <>,
        "" <>,
        "" <>,
        lkml <>,
        Linux OMAP Mailing List <>,
        Discussions about the Letux Kernel 
        <>,,, Aaro Koskinen <>,
        Pavel Machek <>,
        Andrey Gelman <>,
        Haibo Chen <>
Subject: Re: [PATCH v9 1/8] drivers:input:tsc2007: add new common binding
 names, pre-calibration, flipping and rotation


Dne 20.2.2017 v 22:50 Dmitry Torokhov napsal(a):
> On Mon, Feb 20, 2017 at 1:27 PM, H. Nikolaus Schaller <> wrote:
>>> Am 20.02.2017 um 22:08 schrieb Pali Rohár <>:
>>> On Monday 20 February 2017 20:42:15 Pali Rohár wrote:
>>>> Hi Nikolaus!
>>>> On Monday 20 February 2017 17:50:04 H. Nikolaus Schaller wrote:
>>>>> Hi Dmitry,
>>>>>> Input driver may set resolution for given axis in units per mm
>>>>>> (or units per radian for rotational axis ABS_RX, ABS_RY,
>>>>>> ABS_RZ), and if you check the binding, you can use
>>>>>> "touchscreen-x-mm" and "touchscreen-y-mm" to specify the size of
>>>>>> entire touch surface and set resolution from it so that
>>>>>> userspace can calculate the proper scaling factor.
>>>>> How is this information exposed by the kernel to user-space? By
>>>>> scanning the DT file or tree?
>>>> Set input_abs_set_res() from kernel. And in userspace call EVIOCGABS
>>>> ioctl() on input device. Look at struct input_absinfo, you should
>>>> have all needed information here. This is generic input interface,
>>>> no DT is needed.
>>> Looking at kernel code... via EVIOCSABS ioctl() you can even set
>>> resolution from userspace for specified input device.
>>> So this could be potentially used for calibrating input device from
>>> userspace? (In case DT data will not fully match current HW)
>>>> I hope that XServer is already using it for evdev devices...
>>>> For whole implementation look at evtest program. That should be good
>>>> starting point for your userspace implementation.
>>>> While I'm watching this discussion... in my opinion kernel should
>>>> just invert input axes (when needed)
>> It is questionable why it should do that at all then.
> Because the task of the kernel is to provide unified view of the
> hardware. Axis swapping and inversion is needed to that "up" is always
> "up" and "right" is always "right".

Actually my Xorg calibration 3x3 matrix is fine with both axis inverted (on TSC2046).

best regards,

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