Re: [PATCH v2 1/2] dt-bindings: hwmon: add binding documentation for adt7475

[Guenter Roeck]

On 11/17/18 7:29 AM, Rob Herring wrote:
> On Fri, Nov 09, 2018 at 11:56:06AM +1300, Chris Packham wrote:
> > With the addition of the invert-pwm property the adt7475 needs its own
> > binding documentation rather being captured under trivial-devices.txt.
> >
> > Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
> > ---
> > Changes in v2:
> > - use pwm-polarity attiribute to indicate normal or inverted polarity.
> >
> >   .../devicetree/bindings/hwmon/adt7475.txt     | 24 +++++++++++++++++++
> >   .../devicetree/bindings/trivial-devices.txt   |  4 ----
> >   2 files changed, 24 insertions(+), 4 deletions(-)
> >   create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.txt
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.txt b/Documentation/devicetree/bindings/hwmon/adt7475.txt
> > new file mode 100644
> > index 000000000000..d9212b5e9036
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/adt7475.txt
> > @@ -0,0 +1,24 @@
> > +*ADT7475 hwmon sensor.
> > +
> > +Required properties:
> > +- compatible: One of
> > +	"adi,adt7473"
> > +	"adi,adt7475"
> > +	"adi,adt7476"
> > +	"adi,adt7490"
> > +
> > +- reg: I2C address
> > +
> > +optional properties:
> > +
> > +- pwm-polarity: This configures the polarity of the PWM. 0
> > +		(PWM_POLARITY_NORMAL) uses logic high for 100% duty cycle. 1
> > +                (PWM_POLARITY_INVERSED) uses logic low for 100% duty cycle.
>
> So we're using part of the PWM binding, but none of the rest of it? What
> is the PWM connection here?
> The chip has a built-in PWM controller to control fan speeds. PWM frequency
as well as PWM polarity are configurable. I had suggested to use the terminology
from Documentation/devicetree/bindings/pwm/pwm.txt. Other than terminology there
is no connection to a standard pwm controller.

Another option/possibility would be to use a boolean, such as pwm-polarity-inverted.
We are open to suggestions.

> It sounds like this is common for sensors, so this should be documented
> somewhere common.
Sure, no problem. Any suggestion where ?

Thanks,
Guenter