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

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Date:   Sat, 18 Feb 2017 12:33:42 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Welling <mwelling@...e.org>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Igor Grinberg <grinberg@...pulab.co.il>,
        "Andrew F. Davis" <afd@...com>, Mark Brown <broonie@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Alexander Stein <alexander.stein@...tec-electronic.com>,
        Eric Engestrom <eric@...estrom.ch>,
        Hans de Goede <hdegoede@...hat.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Petr Cvek <petr.cvek@....cz>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Nick Dyer <nick@...anahar.org>,
        Siebren Vroegindeweij <siebren.vroegindeweij@...mail.com>,
        Michel Verlaan <michel.verl@...il.com>,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        letux-kernel@...nphoenux.org, linux-iio@...r.kernel.org,
        kernel@...a-handheld.com, Aaro Koskinen <aaro.koskinen@...ia.com>,
        Pali Rohár <pali.rohar@...il.com>,
        Andrey Gelman <andrey.gelman@...pulab.co.il>,
        Haibo Chen <haibo.chen@...escale.com>
Subject: Re: [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation

Hi Pavel,

> Am 18.02.2017 um 10:15 schrieb Pavel Machek <pavel@....cz>:
> 
> 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,
Nikolaus


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