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Date: Wed, 21 Feb 2024 19:27:45 +0000
From: Conor Dooley <conor@kernel.org>
To: Marco Felsch <m.felsch@pengutronix.de>
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: <20240221-imitate-molar-81d93285ac77@spud>
References: <20240221175810.3581399-1-m.felsch@pengutronix.de>
 <20240221-undecided-union-4078db711693@spud>
 <20240221191644.5r3ylr5w3cnfnrzj@pengutronix.de>
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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 lis2m=
dl.
> > >=20
> > > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > > ---
> > >  Documentation/devicetree/bindings/iio/st,st-sensors.yaml | 1 +
> > >  1 file changed, 1 insertion(+)
> > >=20
> > > 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
> >=20
> > Without a fallback compatible to the equivilent device, how does a
> > driver bind to this device?
>=20
> 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.
>=20
> 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.
Besides, having fallback compatibles is the norm when one device has the
same programming model as another.


Cheers,
Conor.


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