Hi Petr and all, > Am 20.02.2017 um 23:26 schrieb Petr Cvek <petr.cvek@xxxxxx>: > > 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. So you probably have exceptionally good eyes and reading a terminal on a touch screen is not a typical use case (except for us hard-core programmers). Anyways, if there is only a single pixel is not accessible due do rescaling and integer truncation effects (which is what Pavel complained) you can still select single letters in a 4x6 font. --- So, let's close commenting this patch here since in my opinion everything is said and the maintainers have decided not to accept it. I hope that I have not forgotten anyone to answer. Thank you very much to all participants for this discussion, because it was really enlightening to me and contains a lot of new perspectives. BR and thanks, Nikolaus-- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
