Hi, > Am 20.02.2017 um 22:50 schrieb Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>: > > On Mon, Feb 20, 2017 at 1:27 PM, H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> wrote: >> >>> Am 20.02.2017 um 22:08 schrieb Pali Rohár <pali.rohar@xxxxxxxxx>: >>> >>> 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". Hm. Why not touching pixel (0,0) on the touch is always pixel (0,0) on the screen and touching pixel (639,479) is always (639,479)? I think it is time to end this discussion. It has show me how much a mess and half-baked area this is, which I did not expect. I read contradicting messages from different people: * don't break user space because it is carved in stone * fix users space if you want to do it properly * scaling by +/-1 and shifting by full range is ok * scaling by ts-size/adc-range and shifting by adc_min is not ok * full numeric ADC resolution is required but subpixel coordinates is not acceptable I will monitor this to see if this becomes sorted out before submitting anything new. BR and thanks, Nikolaus-- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
