Re: [PATCH v2 3/3] dt-bindings: iio: chemical: pms7003: add device tree support

[Johan Hovold <johan@kernel.org>]

On Mon, Jan 28, 2019 at 07:43:33PM +0100, Tomasz Duszynski wrote:
> On Mon, Jan 28, 2019 at 08:58:19AM +0100, Johan Hovold wrote:
> > On Sun, Jan 27, 2019 at 07:19:16PM +0100, Tomasz Duszynski wrote:
> > > Add device tree support for Plantower PMS7003 particulate matter sensor.
> > >
> > > Signed-off-by: Tomasz Duszynski <tduszyns@gmail.com>
> > > ---
> > >  .../iio/chemical/plantower,pms7003.txt        | 19 +++++++++++++++++++
> > >  1 file changed, 19 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.txt
> > >
> > > diff --git a/Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.txt b/Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.txt
> > > new file mode 100644
> > > index 000000000000..e4c7f2fb1e30
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.txt
> > > @@ -0,0 +1,19 @@
> > > +* Plantower PMS7003 particulate matter sensor
> > > +
> > > +Required properties:
> > > +- compatible: must be "plantower,pms7003"
> > > +
> > > +Optional properties:
> > > +- vcc-supply: phandle to the regulator that provides power to the sensor
> >
> > Shouldn't this one be a required property?
> >
> 
> Driver does not use regulator framework hence to me this property fits
> here better.

The device tree describes hardware, not any particular driver.

That said, there is a bit of an on-going debate on whether mandatory
supplies (from a hardware perspective) should always be represented in
device tree or not.

	https://lore.kernel.org/lkml/20181123133126.GF2089@sirena.org.uk/T/#u
        https://lore.kernel.org/lkml/20180409102244.GB11532@sirena.org.uk/T/#u
	https://lore.kernel.org/lkml/20180425171123.xhyoay3nu463btoq@rob-hp-laptop/T/#u

> > > +- set-gpios: phandle to the GPIO connected to the SET line
> > > +- reset-gpios: phandle to the GPIO connected to the RESET line
> > > +
> > > +Refer to serial/slave-device.txt for generic serial attached device bindings.
> > > +
> > > +Example:
> > > +
> > > +&uart0 {
> > > +	pms7003 {
> >
> > The node name should be generic and reflect the functionality rather
> > than model. Perhaps "pms" will do here.
> 
> Agree, ideally we should have a generic dt name for this kind of sensors
> (something like air-pollution-sensor perhaps?). But unfortunately there isn't
> anything available now so I guess compatible part name should be okay
> (besides this is the type of naming commonly used in other iio bindings).

What's wrong with particulate matter sensor ("pms")?

Seems like a better fix than any particular model name to me at least.

> > > +		compatible = "plantower,pms7003";
> > > +	};
> > > +};

Johan