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

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

On Wed, Aug 28, 2024 at 07:36:35AM +0200, Krzysztof Kozlowski wrote:
> On 27/08/2024 23:34, Laurent Pinchart wrote:
> > 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 :-)
> 
> Don't twist our answers. You need fallback, but specific, not family.
> There was a countless number of answers from Rob that specific
> compatibles are preferred.
> 
> Look, Conor's reply:
> 
> https://lore.kernel.org/all/20240620-gating-coherent-af984389b2d7@spud/
> Do you see family fallback? I think "r8a779g0" is SoC.
> 
> Look here:
> https://lore.kernel.org/all/20240610-screen-wolverine-78370c66d40f@spud/
> 
> Or here
> https://lore.kernel.org/all/20240624-rented-danger-300652ab8eeb@wendy/
> where Conor agrees against!
> 
> So let me actually NAK it - you got multiple comments on VIN to use
> specific compatible.

Krzysztof, this tone is not acceptable, regardless of the technical
argument. Period.

Rob, could you please mediate this ?

-- 
Regards,

Laurent Pinchart