Hi Dne 20.2.2017 v 17:50 H. Nikolaus Schaller napsal(a): > Hi Pavel, > >> Am 19.02.2017 um 23:19 schrieb Pavel Machek <pavel@xxxxxx>: >> >> hi! >> >>>>> But as said I don't think we need float or fixed point for practical systems >>>>> at all. >>>> >>>> So you are going to loose precision. And if userspace decides to >>>> calibrate it slightly differently from kernel, lost precision will >>>> matter. >>> >>> Really? >> >> Really. >> >>> Example: >>> >>> ADC values go 100 .. 3995 (i.e. touch margin is 100 steps in pre-calibration) >>> >>> This is scaled to let's say 0..640. >> >> Ok. Now userspace realizes that kernel alignemnt is off, and it would >> want to scale it to 1..642. > > Screen coordinates are still 0..639. > >> That will mean that single pixel will be >> inaccessible, right? > > Yes, that can happen if the additional user-space scale is > 1.0. > > As long as it is small (I expect <1.01 = 1% error in scale) it is > barely noticeable. > > Therefore, I asked before: how big in pixels is your finger or stylus? > Does this effect matter? > > A resistive touch is a man-machine-interface where people press buttons of at > least 12x12 pixels size (or they are no longer visually recognizable). Smallest kernel font is 4x6 (i think) and I'm regularly using 8x8. I would like to be able to select a single letter in the console. cheers, Petr -- 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
