Re: [PATCHv7][ 1/4] Input: tsc2007: Add device tree support.

From: Thierry Reding <thierry.reding@gmail.com>
To: Denis Carikli <denis@eukrea.com>
Cc: "Rob Herring" <rob.herring@calxeda.com>,
	"Shawn Guo" <shawn.guo@linaro.org>,
	"Eric Bénard" <eric@eukrea.com>,
	"Sascha Hauer" <kernel@pengutronix.de>,
	linux-arm-kernel@lists.infradead.org,
	"Grant Likely" <grant.likely@secretlab.ca>,
	"Pawel Moll" <pawel.moll@arm.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Stephen Warren" <swarren@wwwdotorg.org>,
	"Ian Campbell" <ijc+devicetree@hellion.org.uk>,
	devicetree@vger.kernel.org,
	"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
	linux-input@vger.kernel.org,
	"Lothar Waßmann" <LW@KARO-electronics.de>,
	"Linus Walleij" <linus.walleij@linaro.org>
Subject: Re: [PATCHv7][ 1/4] Input: tsc2007: Add device tree support.
Date: Thu, 24 Oct 2013 17:17:37 +0200	[thread overview]
Message-ID: <20131024151736.GE9044@ulmo.nvidia.com> (raw)
In-Reply-To: <1382618536-25320-1-git-send-email-denis@eukrea.com>

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On Thu, Oct 24, 2013 at 02:42:13PM +0200, Denis Carikli wrote:
> Cc: Rob Herring <rob.herring@calxeda.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Stephen Warren <swarren@wwwdotorg.org>
> Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
> Cc: devicetree@vger.kernel.org
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> Cc: Sascha Hauer <kernel@pengutronix.de>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: Lothar Waßmann <LW@KARO-electronics.de>
> Cc: Eric Bénard <eric@eukrea.com>
> Signed-off-by: Denis Carikli <denis@eukrea.com>
> ---
> ChangeLog v6->v7:
> - One small whitespace cleanup.
> - The properties specific to that driver are now prefixed with "ti,".
> - The ti,fuzzy property has now better documentation.
> ---
>  .../bindings/input/touchscreen/tsc2007.txt         |   45 +++++
>  drivers/input/touchscreen/tsc2007.c                |  194 +++++++++++++++-----
>  2 files changed, 198 insertions(+), 41 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
> 
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt b/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
> new file mode 100644
> index 0000000..516b63b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
> @@ -0,0 +1,45 @@
> +* Texas Instruments tsc2007 touchscreen controller
> +
> +Required properties:
> +- compatible: must be "ti,tsc2007".
> +- reg: I2C address of the chip.
> +- ti,x-plate-ohms: X-plate resistance in ohms.
> +
> +Optional properties:
> +- gpios: the interrupt gpio the chip is connected to (trough the penirq pin)
> +  (see GPIO binding[2] for more details).
> +- interrupt-parent: the phandle for the gpio controller
> +  (see interrupt binding[1]).
> +- interrupts: (gpio) interrupt to which the chip is connected
> +  (see interrupt binding[1]).
> +- pinctrl-0: Should specify pin control groups used for the gpio
> +  (see pinctrl bindings[0]).
> +- pinctrl-names: Should contain only one value - "default"
> +  (see pinctrl bindings[0]).

Also I haven't seen a response as to why this can't be handled by the
GPIO driver. Adding Linus Walleij, perhaps he knows a more definitive
answer.

Linus, the issue here is that the pinctrl properties for this chip are
supposed to pinmux the pendown GPIO for this chip. I was under the
impression that this should be handled by the GPIO controller itself, so
that when gpio_request() was called on a pin it would be the GPIO
controller driver's responsibility to pinmux it appropriately.

> +- ti,max-rt: maximum pressure.
> +- ti,fuzzy: specifies the absolute input fuzz value.
> +  If set, it will permit noise in the data up to +- the value given to the fuzz
> +  parameter, that is used to filter noise from the event stream.

Any reason why these can't be specified per axis? From my experience
with this chip it can make sense to use different values for the
different axes. Well, perhaps X and Y axes can share one fuzz factor,
but the Z axis is sometimes different.

You also modify the driver to ignore the X and Z axes fuzz factor even
for platform data where specifying all three separately was explicitly
allowed. Have you verified that this doesn't cause any regressions?

Thierry

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