linux-kernel - Re: [PATCH 23/33] ARM: dts: exynos: Remove empty camera pinctrl configuration in Odroid X/U3

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Message-ID: <01bb90db-511d-fbf5-d29a-1fba932f0abf@samsung.com>
Date:   Mon, 31 Aug 2020 15:57:08 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Sylwester Nawrocki <snawrocki@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Denis GNUtoo Carikli <GNUtoo@...erdimension.org>,
        Simon Shields <simon@...eageos.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 23/33] ARM: dts: exynos: Remove empty camera pinctrl
 configuration in Odroid X/U3

On 31.08.2020 12:42, Krzysztof Kozlowski wrote:
> On Mon, 31 Aug 2020 at 12:35, Sylwester Nawrocki <snawrocki@...nel.org> wrote:
>> On 8/31/20 10:38, Krzysztof Kozlowski wrote:
>>> On Mon, 31 Aug 2020 at 10:31, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
>>>> On 30.08.2020 15:51, Krzysztof Kozlowski wrote:
>>>>> The camera's pinctrl configuration is simply empty and not effective.
>>>>> Remove it to fix dtbs_check warning:
>>>>>
>>>>>     arch/arm/boot/dts/exynos4412-odroidx.dt.yaml: camera: pinctrl-0: True is not of type 'array'
>>>>>
>>>>> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
>>>>
>>>> I think that this was intentional to properly enable support for
>>>> mem-2-mem mode in Exynos4-IS (FIMC), but I'm not sure what are the
>>>> default values if no pinctrl properties are provided. Sylwester, could
>>>> you comment?
>>>
>>> Indeed it could be intentional... I see now errors:
>>> [   33.752203] s5p-fimc-md soc:camera: Failed to get pinctrl: -19
>>>
>>> I wonder why getting an empty pinctrl is needed... maybe the driver
>>> should accept missing pinctrl?
>>
>> It might have been better to have the pinctrl properties optional, as there
>> might be boards without the image sensor attached and FIMC could still be
>> used in memory-to-memory mode, as Marek pointed out. But it seems too late
>> now to change that. The binding defines the pinctrl properties as required
>> (Documentation/devicetree/bindings/media/samsung-fimc.txt) and we need to
>> keep them in dtses.
> 
> You can always make a required property optional and it is not a break
> of ABI. The other way around would be a break. Why then not changing
> the driver to accept optional pinctrl?

Feel free to send the patch, I would prefer to leave that as is though.
Is it really suddenly a problem to use an empty property? The pinctrl 
bindings allows it.

-- 
Regards,
Sylwester