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

From: "Lothar Waßmann" <LW@KARO-electronics.de>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	devicetree@vger.kernel.org,
	"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
	"Eric Bénard" <eric@eukrea.com>,
	"Pawel Moll" <pawel.moll@arm.com>,
	"Stephen Warren" <swarren@wwwdotorg.org>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Ian Campbell" <ijc+devicetree@hellion.org.uk>,
	"Rob Herring" <rob.herring@calxeda.com>,
	"Grant Likely" <grant.likely@secretlab.ca>,
	"Denis Carikli" <denis@eukrea.com>,
	"Sascha Hauer" <kernel@pengutronix.de>,
	linux-input@vger.kernel.org, "Shawn Guo" <shawn.guo@linaro.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCHv7][ 1/4] Input: tsc2007: Add device tree support.
Date: Fri, 25 Oct 2013 08:39:51 +0200	[thread overview]
Message-ID: <20131025083951.18675574@ipc1.ka-ro> (raw)
In-Reply-To: <20131024151736.GE9044@ulmo.nvidia.com>

Hi,

Thierry Reding wrote:
> 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.
> 
When a GPIO is requested the GPIO layer cannot know what it is
requested for and how the pinmux for the pin function should be
configured (pullups, drive strength, ...). A pin may have multiple
functions depending on what modules are plugged into a baseboard.

Thus the pinctrl binding needs to be with the driver that uses the pin.

Lothar Waßmann
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