linux-kernel - Re: [PATCH v3 2/3] Input: cyttsp

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Date:	Mon, 11 Jan 2016 20:01:33 +0100
From:	Oreste Salerno <oreste.salerno@...tom.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Rob Herring <robh@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-input@...r.kernel.org>, <fery@...ress.com>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] Input: cyttsp - add device tree bindings

On Mon, Jan 11, 2016 at 10:45:50AM -0800, Dmitry Torokhov wrote:
> On Mon, Jan 11, 2016 at 06:54:23PM +0100, Oreste Salerno wrote:
> > On Sun, Jan 10, 2016 at 09:01:56PM -0600, Rob Herring wrote:
> > > On Sun, Jan 10, 2016 at 06:36:08PM +0100, Oreste Salerno wrote:
> > > > Signed-off-by: Oreste Salerno <oreste.salerno@...tom.com>
> > > > ---
> > > >  .../bindings/input/touchscreen/cyttsp.txt          |  82 +++++++++++++
> > > >  drivers/input/touchscreen/cyttsp_core.c            | 134 +++++++++++++++++++--
> > > >  include/linux/input/cyttsp.h                       |   3 +
> > > >  3 files changed, 212 insertions(+), 7 deletions(-)
> > > >  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/cyttsp.txt
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/input/touchscreen/cyttsp.txt b/Documentation/devicetree/bindings/input/touchscreen/cyttsp.txt
> > > > new file mode 100644
> > > > index 0000000..2dc5c65
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/input/touchscreen/cyttsp.txt
> > > > @@ -0,0 +1,82 @@
> > > > +* Cypress cyttsp touchscreen controller
> > > > +
> > > > +Required properties:
> > > > +- compatible		: must be "cypress,cyttsp-i2c" or "cypress,cyttsp-spi"
> > > > +- reg			: Device I2C address or SPI chip select number
> > > > +- spi-max-frequency 	: Maximum SPI clocking speed of the device (for cyttsp-spi)
> > > > +- interrupt-parent	: the phandle for the gpio controller
> > > > +			  (see interrupt binding[0]).
> > > > +- interrupts		: (gpio) interrupt to which the chip is connected
> > > > +			  (see interrupt binding[0]).
> > > > +- reset-gpios		: the reset gpio the chip is connected to
> > > > +			  (see GPIO binding[1] for more details).
> > > > +- touchscreen-size-x	: horizontal resolution of touchscreen (in pixels)
> > > > +- touchscreen-size-y	: vertical resolution of touchscreen (in pixels)
> > > > +- bootloader-key	: the 8-byte bootloader key that is required to switch
> > > > +			  the chip from bootloader mode (default mode) to
> > > > +			  application mode.
> > > > +			  This property has to be specified as an array of 8
> > > > +			  '/bits/ 8' values.
> > > > +
> > > > +Optional properties:
> > > > +- active-distance	: the distance in pixels beyond which a touch must move
> > > > +			  before movement is detected and reported by the device.
> > > > +			  Valid values: 0-15.
> > > 
> > > Wouldn't this be the same as touchscreen-fuzz-(x|y) which is the 
> > > replacement for the deprecated moving-threshold? 
> > >
> > 
> > It is somewhat related. But I understand that the touchscreen-fuzz-(x|y) properties
> > are meant to be used as parameters passed to input_set_abs_params(), which are used
> > for a SW-based jitter filtering.
> > The active-distance value instead is used to set a HW register in the chip which
> > effectively performs the filtering in the HW.
> > The driver is currently passing 0 as fuzz parameter to input_set_abs_params().
> 
> It doe snot have to and it will not if you use
> touchscreen_parse_properties(). But you are right, fuzz is reserved for
> software de-jittering, and it can be changed at any time from userspace
> at input device level, but will not be communicated to the hardware. I
> think hardware-based filtering is hardware-specific and I think
> having a separate property is fine for it. We can still standardize on
> name, units, etc though.
>

Yes, I looked at touchscreen_parse_properties and I was planning to use it as part
of a future improvement patch. But it makes sense to introduce it in this patch already.
 
> >  
> > > > +- active-interval-ms	: the minimum period in ms between consecutive
> > > > +			  scanning/processing cycles when the chip is in active mode.
> > > > +			  Valid values: 0-255.
> > > > +- lowpower-interval-ms	: the minimum period in ms between consecutive
> > > > +			  scanning/processing cycles when the chip is in low-power mode.
> > > > +			  Valid values: 0-2550
> > > > +- touch-timeout-ms	: minimum time in ms spent in the active power state while no
> > > > +			  touches are detected before entering low-power mode.
> > > > +			  Valid values: 0-2550
> > > > +
> > > 
> > > Otherwise, looks fine.
> > 
> > I am still waiting for a review from the driver maintainer (Ferruh Yigit), but I see
> > that he hasn't been actively reviewing patches for the cyttsp* drivers for a while.
> > I wonder what would be the process in this case?  
> 
> Please address the items from my other email and I should be able to
> pick it up.
>

OK, I'll try to rework the patch soon and post a new version.
Thanks a lot for your review!

> Thanks.
> 
> -- 
> Dmitry