Re: [PATCH v2 1/6] dt-bindings: media: renesas,isp: Add Gen4 family fallback

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Aug 27, 2024 at 10:12:33AM +0200, Niklas Söderlund wrote:
> On 2024-08-27 08:31:22 +0200, Krzysztof Kozlowski wrote:
> > On Mon, Aug 26, 2024 at 04:43:47PM +0200, Niklas Söderlund wrote:
> > > The ISP Channel Selector IP is the same for all current Gen4 devices.
> > > This was not known when adding support for V3U and V4H and a single SoC
> > > specific compatible was used.
> > > 
> > > Before adding more SoC specific bindings for V4M add a family compatible
> > > fallback for Gen4. That way the driver only needs to be updated once for
> > > Gen4, and we still have the option to fix any problems in the driver if
> > > any testable differences between the SoCs are found.
> > > 
> > > There are already DTS files using the V3U and V4H compatibles which
> > > needs to be updated to not produce a warning for DTS checks. The driver
> > > also needs to kept the compatible values to be backward compatible , but
> > > for new Gen4 SoCs such as V4M we can avoid this.
> > > 
> > > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > > ---
> > > * Changes since v1
> > > - New in v2.
> > > ---
> > >  Documentation/devicetree/bindings/media/renesas,isp.yaml | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/media/renesas,isp.yaml b/Documentation/devicetree/bindings/media/renesas,isp.yaml
> > > index 33650a1ea034..730c86f2d7b1 100644
> > > --- a/Documentation/devicetree/bindings/media/renesas,isp.yaml
> > > +++ b/Documentation/devicetree/bindings/media/renesas,isp.yaml
> > > @@ -22,6 +22,7 @@ properties:
> > >        - enum:
> > >            - renesas,r8a779a0-isp # V3U
> > >            - renesas,r8a779g0-isp # V4H
> > > +      - const: renesas,rcar-gen4-isp # Generic R-Car Gen4
> > 
> > Adding generic fallback post-factum is odd, does not feel reliable.
> > Instead use specific compatibles as fallbacks.
> 
> I agree, it feels a bit odd. But this was the road we hammered out at 
> great pain for how to be able to move forward with this issue for the 
> other IP block involved in video capture for R-Car Gen4, VIN [1]. This 
> just mirrors that long discussion decision for the R-Car CSISP.
> 
> I would hate to have different solutions for the two.
> 
> 1. [PATCH v5 0/6] rcar-vin: Add support for R-Car V4M
>    https://lore.kernel.org/all/20240704161620.1425409-1-niklas.soderlund+renesas@ragnatech.se/

The compatible fallback for VIN has been added following a request from
Conor and Rob, so it would be nice if the three of you could agree to
achieve consistency in the bindings :-)

-- 
Regards,

Laurent Pinchart