Re: [PATCH v3 18/25] dt-bindings: media: imx258: Add alternate compatible strings

[Conor Dooley]

On Fri, Apr 05, 2024 at 11:25:50AM +0100, Dave Stevenson wrote:
> Hi Conor
> 
> On Wed, 3 Apr 2024 at 17:14, Conor Dooley <conor@xxxxxxxxxx> wrote:
> >
> > On Wed, Apr 03, 2024 at 09:03:47AM -0600, git@xxxxxxxxxxxx wrote:
> > > From: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> > >
> > > There are a number of variants of the imx258 modules that can not
> > > be differentiated at runtime, so add compatible strings for the
> > > PDAF variant.
> > >
> > > Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Luis Garcia <git@xxxxxxxxxxxx>
> > > ---
> > >  .../devicetree/bindings/media/i2c/sony,imx258.yaml       | 9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx258.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx258.yaml
> > > index bee61a443b23..c978abc0cdb3 100644
> > > --- a/Documentation/devicetree/bindings/media/i2c/sony,imx258.yaml
> > > +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx258.yaml
> > > @@ -13,11 +13,16 @@ description: |-
> > >    IMX258 is a diagonal 5.867mm (Type 1/3.06) 13 Mega-pixel CMOS active pixel
> > >    type stacked image sensor with a square pixel array of size 4208 x 3120. It
> > >    is programmable through I2C interface.  Image data is sent through MIPI
> > > -  CSI-2.
> > > +  CSI-2. The sensor exists in two different models, a standard variant
> > > +  (IMX258) and a variant with phase detection autofocus (IMX258-PDAF).
> > > +  The camera module does not expose the model through registers, so the
> > > +  exact model needs to be specified.
> > >
> > >  properties:
> > >    compatible:
> > > -    const: sony,imx258
> > > +    enum:
> > > +      - sony,imx258
> > > +      - sony,imx258-pdaf
> >
> > Does the pdaf variant support all of the features/is it register
> > compatible with the regular variant? If it is, the regular variant
> > should be a fallback compatible.
> 
> It has the same register set, but certain registers have to be
> programmed differently so that the image is corrected for the
> partially shielded pixels used for phase detect auto focus (PDAF).
> Either compatible will "work" on either variant of the module, but
> you'll get weird image artifacts when using the wrong one.

To paraphase, a fallback compatible is not suitable.

Thanks Dave,
Conor.

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