linux-kernel - Re: [PATCHv4 2/5] Input: edt-ft5x06: Add DT support

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Message-ID: <20140320132156.GD22115@e106331-lin.cambridge.arm.com>
Date:	Thu, 20 Mar 2014 13:21:56 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Fugang Duan <B38611@...escale.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Henrik Rydberg <rydberg@...omail.se>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Jingoo Han <jg1.han@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Rob Landley <rob@...dley.net>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Simon Budig <simon.budig@...nelconcepts.de>
Subject: Re: [PATCHv4 2/5] Input: edt-ft5x06: Add DT support

On Thu, Mar 20, 2014 at 11:40:55AM +0000, Lothar Waßmann wrote:
> Hi,
> 
> Mark Rutland wrote:
> > On Wed, Mar 19, 2014 at 01:09:20PM +0000, Lothar Waßmann wrote:
> > > 
> > > Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> > > ---
> > >  .../bindings/input/touchscreen/edt-ft5x06.txt      |   41 ++++++
> > >  drivers/input/touchscreen/edt-ft5x06.c             |  144 +++++++++++++++-----
> > >  2 files changed, 154 insertions(+), 31 deletions(-)
> > >  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> > > 
> > > diff --git a/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> > > new file mode 100644
> > > index 0000000..e5adc76
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> > > @@ -0,0 +1,41 @@
> > > +FocalTech EDT-FT5x06 Polytouch driver
> > > +=====================================
> > > +
> > > +Required properties:
> > > + - compatible:  "edt,edt-ft5x06"
> > 
> > Is the 'x' part of a particular product name, or is this a class of
> > devices?
> > 
> The FT5x06 datasheet lists 3 variants for different panel sizes.
> I'll add distinct compatible strings for those chips, though their SW
> interface is (currently) identical:
> |Required properties:
> | - compatible:  "edt,edt-ft5206", "edt,edt-ft5x06"
> |           or:  "edt,edt-ft5306", "edt,edt-ft5x06"
> |           or:  "edt,edt-ft5406", "edt,edt-ft5x06"

Drop the "edt,edt-ft5x06" string. If they really appear to be identical
from a programmer's perspective, choose a particular variant to be used
as the fallback.

There could be a future variant that would appear to match the x string
yet was completely incompatible with the expected programming interface.

> > > + - reg:         I2C slave address of the chip (0x38)
> > > + - interrupt-parent: a phandle pointing to the interrupt controller
> > > +                     serving the interrupt for this chip
> > > + - interrupts:       interrupt specification for this chip
> > 
> > How many? What are they for?
> >
> I'll change it to: 
> | - interrupts:       interrupt specification for the touchdetect
> |                     interrupt

That sounds fine to me.

> > > + - report_rate: allows setting the report rate in the range from 3 to
> > > +                14.
> > 
> > However, why can the kernel not decide the report rate? This doesn't
> > sound like something that needs to vary per-board.
> > 
> > Also, s/_/-/ in property names, please.
> > 
> OK, I'll drop the property, which also simplyfies the code a bit.

Sounds good to me.

> 
> > > +#define EDT_GET_PROP(name, reg) {					\
> > > +	const u32 *prop = of_get_property(np, #name, NULL);		\
> > > +	if (prop)							\
> > > +		edt_ft5x06_register_write(tsdata, reg, be32_to_cpu(*prop)); \
> > > +}
> > 
> > Use of_property_read_u32, it'll handle endianness conversion for you.
> > 
> > Use of of_get_property is almost always wrong.
> > 
> Sure.

Cheers,
Mark.
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