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

From: H. Nikolaus Schaller
Date: Sat Feb 18 2017 - 06:34:06 EST

Hi Pavel,

> Am 18.02.2017 um 10:15 schrieb Pavel Machek <pavel@xxxxxx>:
> Hi!
>>> Well, there is some historic confusion wether this driver reports resistance
>>> or pressure.
>>> The unpatched tsc2007 driver does it wrong (please test!) and we fix it on
>>> the fly (because a separate patch is much more complex than doing it right
>>> immediately).
>>> This ti,report-resistance property is a means to get the old (wrong) meaning back
>>> in case someone urgently needs it and can't fix the user-space workaround which
>>> he must be using.
>>> AFAIK there is no mainline board using the DT except ours (and the upcoming
>>> OMAP5-Pyra), so we shouldn't care too much. If you prefer, you can remove this
>>> compatibility property. We don't need it for our devices.
> N900 is mainline and uses DT.

Yes, but it does not use the tsc2007 and will not be influenced at all by this patch.

>>> That the function name is wrong is a second issue and this double negation might
>>> confuse a litte.
>>> Please test on a real device if the patched driver reports pressure now (unless
>>> ti,report-resistance is specified).
>> I unfortunately can not test this driver as I do not have the hardware.
>> So all my observations are from code and data sheets.
>> That said, what is the values emitted as ABS_PRESSURE when finger is not
>> touching the device, barely touching the device, or pressing firmly?
>> It seems that between TSC2007, TSC2004, TSC2005, and ADS7846, we have
>> confusion as to what is being reported.
>> I am adding a few more folks to the CC so we can try and soft this out.
>> Sebastian, Pali, Pavel, any input here?
> X work ok on N900. Nikolaus wrote rather long email, but I'm not what
> the meaning is and what is supposed to be broken there.

IMHO it is broken that you have to do a subtle calibration step in user-space
and repeat it for different GUI toolkits.

> I do this on X startup:
> xinput --set-prop --type=float "TSC200X touchscreen" "Coordinate Transformation Matrix" 1.10 0.00 -0.05 0.00 1.18 -0.10 0.00 0.00 1.00
> xinput --set-prop --type=int "TSC200X touchscreen" "Evdev Axis Inversion" 0 1
> xinput --set-prop --type=float "TSC2005 touchscreen" "Coordinate Transformation Matrix" 1\
> .10 0.00 -0.05 0.00 1.18 -0.10 0.00 0.00 1.00
> xinput --set-prop --type=int "TSC2005 touchscreen" "Evdev Axis Inversion" 0 1

Wouldn't it be nice to get rid of this completely, because the DT/kernel knows these
factors? Especially since they are well defined by the hardware?

> And I agree that kernel should _not_ attempt rescaling itself, as it
> would lose precision.

With an almost 1:1 mapping you won't loose precision.

> Providing default calibration info is ok.

IMHO it is missing one step of automation.

BR and thanks,

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