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

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Message-ID: <20170219221930.GA1568@amd>
Date:   Sun, 19 Feb 2017 23:19:30 +0100
From:   Pavel Machek <pavel@....cz>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
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!

> >> 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. That will mean that single pixel will be
inaccessible, right?

> > No. You have to design interface such that they _can_ be improved, and
> > what you propose does not work that way.
> 
> It works. Please do real world tests...

You do a real world test on N900, and propose upgrade path.

> > Yes. I want to prevent you from pushing crap into the kernel.
> 
> Crap? Well, we have discussed this driver for months here on the list and
> after a lot of improvements we came up to v9.
> 
> And you still think it is crap and none of the other reviewers has noticed?

I'm pretty sure you will not be able to push calibration into kernel.

> > Userspace has to know how to do the calibration _anyway_ (for
> > other hardware),
> 
> What for? I do not understand which other hardware you are talking about.
> 
> On our devices there is only one touch glued to the panel and that one
> has to be calibrated. Ideally before the user gets the device into his
> hands => precalibration...
> 
> If you connect a digitizer, then that one has to be calibrated of course,
> but it is not glued onto the display panel. Hence it is a different
> issue.

It is actually same issue. One kernel interface should work for all
the touchscreens.

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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