Re: [Letux-kernel] [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation

Andreas Kemnade
2017-02-21T17:10:21Z

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Hi,

[...]
> > 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)?
>
> Important is that there is no 1:1 mapping between input evdev device
> and drm/fb output device. These are two independent devices. There is
> no connection between screen and touch. So such presumption should
> not be done in kernel. You can do that in userspace.
>
But at least it can be told to userspace that these two devices are
connected. That information should be specified in devicetree because
it is not auto-detectable.

> Lets take e.g. touchpad. It acts similarly as touchscreen input device
> (both reports absolute positioned touch events), but touchpad is not
> connected with screen. And from kernel point of view these devices are
> both input and absolute positioned.
>
> It looks like the whole problem is there that you wanted to do this
> mapping for your hardware in kernel. And this is not what is kernel
> doing or should do. Moreover I know people who are using integrated
> touchscreen on laptop as (touch) input device for external monitor.
> And in this configuration it does not make any sense to map
> touchscreen input to pixels of integrated LCD touchscreen (as
> external monitor could have different resolution as integrated LCD
> touchcreen).
>
Interesting example. But then you also do not need flipping/rotation
because the angle between your screen and your absolute position device
is not fixed.

Regards,
Andreas

>

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