Hi Jens, On Fri, Feb 27, 2015 at 1:41 AM, Jens Thiele <[email protected]> wrote: > Hi Tsvetan, > > maybe you can shed some light on this. > > Hans de Goede <[email protected]> writes: > >> Hi, >> >> On 26-02-15 11:41, Jens Thiele wrote: >>> the problem i see: >>> at least the touch screens i have got all differ in quality/sensitivity >>> => imho a static assignment via devicetree won't really cut it (but yes >>> it would make adjustment easier). >> >> Well devicetree files are per board / tablet, so when creating the dts >> files the brand / model of touchscreen is known, and I would expect >> the sensitivity to be constant for the same brand/model touchscreen. > > My experience with the Olimex LCD displays is different (so far). > I have got: > 2* A13-LCD7-TS differing in quality (the older one having the "better" > touch screen) > > A A13-LCD10TS and a LCD-OLinuXino-10TS. Okay those are different models, > but I somehow hoped the LCD-OLinuXino-10TS would be a A13-LCD10TS + the > additional ports for the lime/lime2. > > The A13-LCD10TS (I have) is the one that definitely needs the > sensitivity adjustment. > > The A13-LCD10TS is matte and the LCD-OLinuXino-10TS is unfortunately > glossy. > > @Tsvetan: > > does Olimex have multiple display/touch screen suppliers? > > did you see the quality difference with the A13-LCD7-TS, too? > > Can you give any "guarantees" (please don't take that in any way as a > legal thing) about the quality of future displays? will they stay the > same model? The LCD-OLinuXino-10TS I just got, has a "ARISING" label on > the back. > > And finally to get really back on topic: > > Do you think it is reasonable to expect the display/touchscreen of two > Allwinner based tablets sold by the same name (including model number) > are identical, or do they use different displays / touchscreen elements > all the time?
I think the answer is "It depends" I have two Allwinner SoC based tablets, one is a "generic" board that has been put into at least three different tablets I'm aware of. The FEX file and Android instance for it have configuration and drivers for at least three different models of touch screen. The other is manufactured by HP and I believe that while the particular board is put into at least 2 different models, they're all slight variations on the same thing (different / cheaper LCD) and consequently should all have the same touch screen chip. I think the general consensus is that one can assume that all tablets with the same name and details will have the same touch screen. In your case, with development boards, that's less viable and we possibly should be using device tree overlays (or whatever they're called) to separate peripheral configuration (the LCD + touch screen board) from system configuration (the development board itself) but I'm hazy on the details. IMHO, you should write the patch to get the value from device tree and worry about the board configuration details when submitting that. Thanks, -- Julian Calaby Email: [email protected] Profile: http://www.google.com/profiles/julian.calaby/ -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
