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[85.230.190.116]) by smtp.gmail.com with ESMTPSA id g11sm424460lfg.31.2019.02.01.01.12.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 Feb 2019 01:12:33 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.91) (envelope-from ) id 1gpUsB-0003LP-Ad; Fri, 01 Feb 2019 10:12:31 +0100 Date: Fri, 1 Feb 2019 10:12:31 +0100 From: Johan Hovold To: Tomasz Duszynski Cc: Johan Hovold , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, robh@kernel.org, jic23@jic23.retrosnub.co.uk Subject: Re: [PATCH v2 3/3] dt-bindings: iio: chemical: pms7003: add device tree support Message-ID: <20190201091231.GZ3691@localhost> References: <20190127181916.19948-1-tduszyns@gmail.com> <20190127181916.19948-4-tduszyns@gmail.com> <20190128075819.GK3691@localhost> <20190128184332.GA25627@arch> <20190130091254.GN3691@localhost> <20190131204000.GA14750@arch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190131204000.GA14750@arch> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, Jan 31, 2019 at 09:40:04PM +0100, Tomasz Duszynski wrote: > On Wed, Jan 30, 2019 at 10:12:54AM +0100, Johan Hovold wrote: > > 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 > > > > > --- > > > > > .../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 > > > > Even after going through this threads I am still unconvinced that > vcc-supply should be a requirement. Making this a mandatory property > would automatically imply using *_regulator_get() in a driver code > (on condition one is adding regulator support). In case there > isn't any physically connected we end up with a dummy one and a warning. How would the device work at all without a physical vcc supply? > Is it how this should work? As Mark mentioned in the threads above, you could add a fixed, always-on regulator for cases where the device is always powered. Boards failing to describe this supply would still work on Linux, but would end up with a dummy regulator and a warning. > > > > > +- 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. > > > > Personally I would vote for a more descriptive node name, for example: > particulate-matter-sensor or air-pollution-sensor or other name > which clearly shows what device we are dealing with. Spelling it out seems preferable, yes. You know the domain better than I do; I only suggest you come up with a generic node name. Johan