linux-kernel - Re: [PATCH v2 3/4] media: dt-bindings: add bindings for Toshiba TC358746

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Message-ID: <8e54e03e-105a-cf3e-242f-796bef77bfe1@linaro.org>
Date:   Wed, 21 Sep 2022 10:59:04 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        devicetree@...r.kernel.org, jacopo@...ndi.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        kieran.bingham+renesas@...asonboard.com,
        linux-kernel@...r.kernel.org, kishon@...com, hverkuil@...all.nl,
        vkoul@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-phy@...ts.infradead.org,
        mchehab@...nel.org, kernel@...gutronix.de,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v2 3/4] media: dt-bindings: add bindings for Toshiba
 TC358746

On 21/09/2022 10:35, Marco Felsch wrote:
> On 22-09-21, Krzysztof Kozlowski wrote:
>> On 20/09/2022 19:32, Laurent Pinchart wrote:
>>>>>
>>>>> Explicit bus types in DT indeed makes it easier for drivers, so if a
>>>>> device can support multiple bus types (even if not implemented yet in
>>>>> the corresponding drivers), the property should be there.
>>>>
>>>> Okay, I will make it required.
>>>>
>>>>>> Why do you have hsync-active and vsync-active if both are always zero? Can
>>>>>> the hardware not support other configuration?
>>>>
>>>> Sure the device supports toggling the logic but it is not implemented.
>>>> So the bindings needs to enforce it to 0 right now. As soon as it is
>>>> implemented & tested, we can say that both is supported :)
>>>
>>> Bindings are not supposed to be limited by the existing driver
>>> implementation, so you can already allow both polarities, and just
>>> reject the unsupported options in the driver at probe time. Future
>>> updates to the driver won't require a binding change.
>>>
>>
>> +1
> 
> I don't wanna do that because this let the binding user assume that
> this mode is already supported. 

What do you mean by "not supported"? By which system? By which firmware
element? Bindings are used by several operating systems and several
projects.

That's not the argument.

Bindings should be complete. Lack of knowledge and datasheets is a good
exception from this rule. Looking at Linux driver is not good exception.

> Adapting a binding is just 1 commit and
> since the property is already existing, there is no breaking change.
Best regards,
Krzysztof