linux-kernel - Re: [PATCH v2 5/6] can: tcan4x5x: Add support for tcan4552/4553

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Message-ID: <20230718-marigold-violation-8d40e9d264c2-mkl@pengutronix.de>
Date:   Tue, 18 Jul 2023 09:57:49 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Markus Schneider-Pargmann <msp@...libre.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Conor Dooley <conor+dt@...nel.org>,
        Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Michal Kubiak <michal.kubiak@...el.com>,
        Vivek Yadav <vivek.2311@...sung.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH v2 5/6] can: tcan4x5x: Add support for tcan4552/4553

On 01.07.2023 10:34:00, Krzysztof Kozlowski wrote:
> On 27/06/2023 16:23, Markus Schneider-Pargmann wrote:
> 
> >>> The version information is always readable for that chip, regardless of
> >>> state and wake GPIOs as far as I know. So yes it is possible to setup
> >>> the GPIOs based on the content of the ID register.
> >>>
> >>> I personally would prefer separate compatibles. The binding
> >>> documentation needs to address that wake and state GPIOs are not
> >>> available for tcan4552/4553. I think having compatibles that are for
> >>> these chips would make sense then. However this is my opinion, you are
> >>> the maintainer.
> >>
> >> We do not talk about compatibles in the bindings here. This is
> >> discussion about your driver. The entire logic of validating DTB is
> >> flawed and not needed. Detect the variant and act based on this.
> > 
> > I thought it was about the bindings, sorry.
> > 
> > So to summarize the compatibles ti,tcan4552 and ti,tcan4553 are fine.
> > But the driver should use the ID register for detection and not compare
> > the detected variant with the given compatible?
> > 
> > In my opinion it is useful to have an error messages that says there is
> > something wrong with the devicetree as this can be very helpful for the
> > developers who bringup new devices. This helps to quickly find issues
> > with the devicetree.
> 
> That's not a current policy for other drivers, so this shouldn't be
> really special. Kernel is poor in validating DTS. It's not its job. It's
> the job of the DT schema.

Fine with me.

I decided to have a check of the auto-detected chip variant against the
specified one in the mcp251xfd driver, as it widely used with raspi
boards, where commonly DT overlays are used. It also helps remote
diagnostics of people, who don't focus on kernel development.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
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