From: "H. Nikolaus Schaller" <hns@goldelico.com>
To: "Petr Cvek" <petr.cvek@tul.cz>,
"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
"Pavel Machek" <pavel@ucw.cz>,
"Sebastian Reichel" <sre@kernel.org>,
"Pali Rohár" <pali.rohar@gmail.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
"Benoît Cousson" <bcousson@baylibre.com>,
"Tony Lindgren" <tony@atomide.com>,
"Russell King" <linux@armlinux.org.uk>,
"Arnd Bergmann" <arnd@arndb.de>,
"Michael Welling" <mwelling@ieee.org>,
"Mika Penttilä" <mika.penttila@nextfour.com>,
"Javier Martinez Canillas" <javier@osg.samsung.com>,
"Igor Grinberg" <grinberg@compulab.co.il>,
"Andrew F. Davis" <afd@ti.com>, "Mark Brown" <broonie@kernel.org>,
"Jonathan Cameron" <jic23@kernel.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Alexander Stein" <alexander.stein@systec-electronic.com>,
"Eric Engestrom" <eric@engestrom.ch>,
"Hans de Goede" <hdegoede@redhat.com>,
"Benjamin Tissoires" <benjamin.tissoires@redhat.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Hans Verkuil" <hans.verkuil@cisco.com>,
"Nick Dyer" <nick@shmanahar.org>,
"Siebren Vroegindeweij" <siebren.vroegindeweij@hotmail.com>,
"Michel Verlaan" <michel.verl@gmail.com>,
linux-input@vger.kernel.org,
devicetree <devicetree@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-omap <linux-omap@vger.kernel.org>,
"Discussions about the Letux Kernel"
<letux-kernel@openphoenux.org>,
linux-iio@vger.kernel.org, kernel@pyra-handheld.com,
"Aaro Koskinen" <aaro.koskinen@nokia.com>,
"Andrey Gelman" <andrey.gelman@compulab.co.il>,
"Haibo Chen" <haibo.chen@freescale.com>
Subject: Re: [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation
Date: Tue, 21 Feb 2017 09:29:53 +0100 [thread overview]
Message-ID: <EABA13E3-05E4-4A7B-A84D-033BB8FBDE28@goldelico.com> (raw)
In-Reply-To: <e3dd020e-8590-6e65-9151-b5f1492debcb@tul.cz>
Hi Petr and all,
> Am 20.02.2017 um 23:26 schrieb Petr Cvek <petr.cvek@tul.cz>:
>
> Hi
>
> Dne 20.2.2017 v 17:50 H. Nikolaus Schaller napsal(a):
>> Hi Pavel,
>>
>>> Am 19.02.2017 um 23:19 schrieb Pavel Machek <pavel@ucw.cz>:
>>>
>>> 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.
>>
>> Screen coordinates are still 0..639.
>>
>>> That will mean that single pixel will be
>>> inaccessible, right?
>>
>> Yes, that can happen if the additional user-space scale is > 1.0.
>>
>> As long as it is small (I expect <1.01 = 1% error in scale) it is
>> barely noticeable.
>>
>> Therefore, I asked before: how big in pixels is your finger or stylus?
>> Does this effect matter?
>>
>> A resistive touch is a man-machine-interface where people press buttons of at
>> least 12x12 pixels size (or they are no longer visually recognizable).
>
> Smallest kernel font is 4x6 (i think) and I'm regularly using 8x8. I would like
> to be able to select a single letter in the console.
So you probably have exceptionally good eyes and reading a terminal on a touch
screen is not a typical use case (except for us hard-core programmers).
Anyways, if there is only a single pixel is not accessible due do rescaling and integer
truncation effects (which is what Pavel complained) you can still select single letters
in a 4x6 font.
---
So, let's close commenting this patch here since in my opinion everything is said
and the maintainers have decided not to accept it.
I hope that I have not forgotten anyone to answer.
Thank you very much to all participants for this discussion, because it was
really enlightening to me and contains a lot of new perspectives.
BR and thanks,
Nikolaus
next prev parent reply other threads:[~2017-02-21 8:30 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-28 14:53 [PATCH v9 0/8] drivers: touchscreen: tsc2007 and ads7846/tsc2046 improvements (use common touchscreen bindings, pre-calibration, spi fix and provide iio raw values) H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation H. Nikolaus Schaller
2017-01-09 17:43 ` Rob Herring
2017-01-28 19:33 ` Dmitry Torokhov
2017-01-28 21:44 ` H. Nikolaus Schaller
2017-02-17 20:40 ` Dmitry Torokhov
2017-02-18 3:22 ` Sebastian Reichel
2017-02-18 11:33 ` H. Nikolaus Schaller
2017-02-18 23:44 ` Sebastian Reichel
2017-02-19 12:07 ` H. Nikolaus Schaller
2017-02-19 20:15 ` Sebastian Reichel
2017-02-20 16:49 ` H. Nikolaus Schaller
2017-02-18 7:45 ` [Letux-kernel] " Andreas Kemnade
2017-02-18 9:15 ` Pavel Machek
2017-02-18 11:33 ` H. Nikolaus Schaller
2017-02-18 18:08 ` Pavel Machek
2017-02-18 19:17 ` H. Nikolaus Schaller
2017-02-18 22:54 ` Pavel Machek
2017-02-19 12:05 ` H. Nikolaus Schaller
2017-02-19 14:17 ` Pavel Machek
2017-02-19 17:04 ` H. Nikolaus Schaller
2017-02-19 17:15 ` Pavel Machek
2017-02-19 17:51 ` H. Nikolaus Schaller
2017-02-19 19:05 ` Pavel Machek
2017-02-19 19:31 ` H. Nikolaus Schaller
2017-02-19 20:57 ` Pavel Machek
2017-02-19 22:01 ` H. Nikolaus Schaller
2017-02-19 22:19 ` Pavel Machek
2017-02-20 16:50 ` H. Nikolaus Schaller
2017-02-20 19:29 ` Pavel Machek
2017-02-20 20:20 ` H. Nikolaus Schaller
2017-02-20 22:26 ` Petr Cvek
2017-02-21 8:29 ` H. Nikolaus Schaller [this message]
2017-02-19 22:29 ` [Letux-kernel] " Andreas Kemnade
2017-02-19 22:39 ` Pavel Machek
2017-02-20 16:50 ` H. Nikolaus Schaller
2017-02-20 19:32 ` Pavel Machek
2017-02-20 20:22 ` H. Nikolaus Schaller
2017-02-20 20:50 ` H. Nikolaus Schaller
2017-02-18 11:32 ` H. Nikolaus Schaller
2017-02-20 1:07 ` Dmitry Torokhov
2017-02-20 16:50 ` H. Nikolaus Schaller
2017-02-20 19:42 ` Pali Rohár
2017-02-20 20:35 ` H. Nikolaus Schaller
2017-02-20 21:07 ` Pali Rohár
2017-02-20 21:24 ` H. Nikolaus Schaller
2017-02-20 21:54 ` Pali Rohár
2017-02-21 6:42 ` H. Nikolaus Schaller
2017-02-21 8:53 ` Pali Rohár
2017-02-20 21:08 ` Pali Rohár
2017-02-20 21:27 ` H. Nikolaus Schaller
2017-02-20 21:50 ` Dmitry Torokhov
2017-02-20 22:21 ` Petr Cvek
2017-02-20 22:24 ` Dmitry Torokhov
2017-02-21 6:56 ` H. Nikolaus Schaller
2017-02-20 22:45 ` Pali Rohár
2017-02-21 6:36 ` H. Nikolaus Schaller
2017-02-21 9:09 ` Pali Rohár
2017-02-21 17:07 ` [Letux-kernel] " Andreas Kemnade
2017-02-20 22:04 ` Pali Rohár
2017-02-21 6:49 ` H. Nikolaus Schaller
2017-02-21 7:14 ` H. Nikolaus Schaller
2017-02-21 8:47 ` Pali Rohár
2017-02-21 8:57 ` [Letux-kernel] " Christ van Willegen
2017-02-21 11:07 ` Pavel Machek
2016-12-28 14:53 ` [PATCH v9 2/8] drivers:input:tsc2007: check for presence and power down tsc2007 during probe H. Nikolaus Schaller
2017-02-17 20:52 ` Dmitry Torokhov
2016-12-28 14:53 ` [PATCH v9 3/8] DT:omap3+tsc2007: use new common touchscreen bindings H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 4/8] drivers:input:ads7846(+tsc2046): add new common binding names, pre-calibration and flipping H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 5/8] dt-bindings: input: move ads7846 bindings to touchscreen subdirectory H. Nikolaus Schaller
2017-02-23 9:54 ` H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 6/8] drivers:input:ads7846(+tsc2046): fix spi module table H. Nikolaus Schaller
2017-01-28 19:35 ` Dmitry Torokhov
2017-01-29 8:39 ` H. Nikolaus Schaller
2017-01-29 18:01 ` Dmitry Torokhov
2017-01-29 18:25 ` H. Nikolaus Schaller
2017-02-01 20:20 ` H. Nikolaus Schaller
2017-02-01 21:14 ` Javier Martinez Canillas
2017-02-01 22:28 ` Dmitry Torokhov
2017-02-01 22:50 ` Javier Martinez Canillas
2017-02-02 5:47 ` H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 7/8] DT:omap3+ads7846: use new common touchscreen bindings H. Nikolaus Schaller
2016-12-28 14:53 ` [PATCH v9 8/8] drivers:input:tsc2007: add iio interface to read external ADC input and temperature H. Nikolaus Schaller
2016-12-30 20:36 ` Jonathan Cameron
2017-02-17 21:27 ` Dmitry Torokhov
2017-02-18 11:35 ` H. Nikolaus Schaller
2017-01-16 6:34 ` [PATCH v9 0/8] drivers: touchscreen: tsc2007 and ads7846/tsc2046 improvements (use common touchscreen bindings, pre-calibration, spi fix and provide iio raw values) H. Nikolaus Schaller
2017-01-21 13:08 ` Jonathan Cameron
2017-01-21 13:17 ` H. Nikolaus Schaller
2017-01-28 18:16 ` [Letux-kernel] " H. Nikolaus Schaller
2017-02-12 15:18 ` H. Nikolaus Schaller
2017-02-15 14:03 ` H. Nikolaus Schaller
2017-02-17 20:43 ` Dmitry Torokhov
2017-02-18 11:30 ` H. Nikolaus Schaller
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