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Date: Wed, 21 Feb 2024 20:45:18 +0100
From: Marco Felsch <m.felsch@pengutronix.de>
To: Conor Dooley <conor@kernel.org>
Cc: jic23@kernel.org, lars@metafoo.de, robh+dt@kernel.org,
	krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
	denis.ciocca@st.com, linus.walleij@linaro.org,
	linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel@pengutronix.de
Subject: Re: [PATCH] dt-bindings: iio: st-sensors: Add IIS2MDC magnetometer
Message-ID: <20240221194518.3sm4o5i274ldpvzf@pengutronix.de>
References: <20240221175810.3581399-1-m.felsch@pengutronix.de>
 <20240221-undecided-union-4078db711693@spud>
 <20240221191644.5r3ylr5w3cnfnrzj@pengutronix.de>
 <20240221-imitate-molar-81d93285ac77@spud>
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In-Reply-To: <20240221-imitate-molar-81d93285ac77@spud>

Hi Conor,

On 24-02-21, Conor Dooley wrote:
> On Wed, Feb 21, 2024 at 08:16:44PM +0100, Marco Felsch wrote:
> > On 24-02-21, Conor Dooley wrote:
> > > On Wed, Feb 21, 2024 at 06:58:10PM +0100, Marco Felsch wrote:
> > > > Add the iis2mdc magnetometer support which is equivalent to the lis2mdl.
> > > > 
> > > > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > > > ---
> > > >  Documentation/devicetree/bindings/iio/st,st-sensors.yaml | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/iio/st,st-sensors.yaml b/Documentation/devicetree/bindings/iio/st,st-sensors.yaml
> > > > index fff7e3d83a02..ee593c8bbb65 100644
> > > > --- a/Documentation/devicetree/bindings/iio/st,st-sensors.yaml
> > > > +++ b/Documentation/devicetree/bindings/iio/st,st-sensors.yaml
> > > > @@ -64,6 +64,7 @@ properties:
> > > >            - st,lsm9ds0-gyro
> > > >        - description: STMicroelectronics Magnetometers
> > > >          enum:
> > > > +          - st,iis2mdc
> > > 
> > > Without a fallback compatible to the equivilent device, how does a
> > > driver bind to this device?
> > 
> > I skimed the datasheets and the driver already handles this binding
> > exactly the same as the st,lis2mdl, so my assumption is they do match.
> > 
> > Why do I you think we need a fallback compatible here?
> 
> I didn't look at the driver, there was no mention of the driver already
> having (undocumented) support for it. Since there was no driver change
> alongside this patch, I thought you'd need a fallback compatible to
> allow the driver to match against a compatible it recognises.

I explicitly did not mention the driver in the commit message else I
would have got a response like "dt-bindings have no dependency to
drivers" ;)

> Besides, having fallback compatibles is the norm when one device has the
> same programming model as another.

Not for this binding according the driver.

Regards,
  Marco

> 
> 
> Cheers,
> Conor.
>