From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pali =?utf-8?q?Roh=C3=A1r?= <pali.rohar@gmail.com>
Subject: Re: [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation
Date: Mon, 20 Feb 2017 23:04:22 +0100
Message-ID: <201702202304.22964@pali>
References: <cover.1482936802.git.hns@goldelico.com> <201702202208.50498@pali> <C2E7AC24-75AB-442F-94A2-84904723EE41@goldelico.com>
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To: "H. Nikolaus Schaller" <hns@goldelico.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>, Sebastian Reichel <sre@kernel.org>, Mark Rutland <mark.rutland@arm.com>, =?utf-8?q?Beno=C3=AEt_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 =?utf-8?q?Penttil=C3=A4?= <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 <benjam>
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On Monday 20 February 2017 22:27:39 H. Nikolaus Schaller wrote:
> > Am 20.02.2017 um 22:08 schrieb Pali Roh=C3=A1r <pali.rohar@gmail.com>:
> >=20
> > On Monday 20 February 2017 20:42:15 Pali Roh=C3=A1r wrote:
> >> While I'm watching this discussion... in my opinion kernel should
> >> just invert input axes (when needed)
>=20
> It is questionable why it should do that at all then.
>=20
> User-Space can also easily do it. Either the driver should provide
> raw data only or if it does pre-processing (scaling by +/-1), why
> exclude pre-scaling by other factors?

Via resolution property which is in that EVIOCSABS ioctl() you specify=20
value which represent unit per mm. So you cannot do full rescaling like=20
via affine transformation. Specially you cannot swap axes or invert it.

As such thing is not supported by current kernel <--> userspace API it=20
needs to be done in kernel.

Moreover I see that this is already handled by kernel's of_touchscreen.c=20
code via DT properties: touchscreen-inverted-* touchscreen-swapped-x-y

And... I'm not sure but I think that linux exports absolute input=20
devices with coordinates where point (0,0) is mapped as left upper=20
corner.

> >> and should not do any other
> >> normalization or integer/floating-point
> >> re-calibration/re-calculation. If it correctly exports minimum
> >> value, maximum value and resolution then userspace can correctly
> >> re-scale input events to units which userspace needs (e.g. mapping
> >> into LCD screen pixels or whatever is needed).

=2D-=20
Pali Roh=C3=A1r
pali.rohar@gmail.com

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