Date:   Tue, 8 Sep 2020 11:10:25 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Sakari Ailus <sakari.ailus@....fi>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <hverkuil@...all.nl>, <jacopo+renesas@...ndi.org>,
        <luca@...aceresoli.net>, <leonl@...pardimaging.com>,
        <robh+dt@...nel.org>, <lgirdwood@...il.com>, <broonie@...nel.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/3] dt-bindings: media: imx274: Add optional input
 clock and supplies


On 9/8/20 7:34 AM, Jacopo Mondi wrote:
> Hi Sakari, Sowjanya,
>
> On Tue, Sep 08, 2020 at 12:33:41PM +0300, Sakari Ailus wrote:
>> On Thu, Sep 03, 2020 at 09:40:57AM -0700, Sowjanya Komatineni wrote:
>>> On 9/3/20 9:35 AM, Jacopo Mondi wrote:
>>>> Hi Sowjanya,
>>>>
>>>> On Thu, Sep 03, 2020 at 09:05:27AM -0700, Sowjanya Komatineni wrote:
>>>>> On 9/3/20 5:55 AM, Jacopo Mondi wrote:
>>>>>> Hello Sowjanya,
>>>>>>
>>>>>> On Tue, Sep 01, 2020 at 07:04:37PM -0700, Sowjanya Komatineni wrote:
>>>>>>> This patch adds IMX274 optional external clock input and voltage
>>>>>>> supplies to device tree bindings.
>>>>>>>
>>>>>>> Reviewed-by: Luca Ceresoli <luca@...aceresoli.net>
>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>>>>>> ---
>>>>>>>     .../devicetree/bindings/media/i2c/sony,imx274.yaml  | 21 +++++++++++++++++++++
>>>>>>>     1 file changed, 21 insertions(+)
>>>>>>>
>>>>>>> diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
>>>>>>> index 7ae47a6..57e7176 100644
>>>>>>> --- a/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
>>>>>>> +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
>>>>>>> @@ -25,6 +25,27 @@ properties:
>>>>>>>       reset-gpios:
>>>>>>>         maxItems: 1
>>>>>>>
>>>>>> I just sent an update to my json-schema conversion of this bindings
>>>>>> document (not yet on patchwork, sorry) and Sakari pointed me to the
>>>>>> fact in between my v2 and my v4 this patch from you went in:
>>>>>> 4ea3273d24b ("dt-bindings: media: imx274: Add optional input clock and supplies")
>>>>>>
>>>>>> I should probably now update my bindings conversion patch, basically
>>>>>> taking in what you've done here, but I would have one question.
>>>>>>
>>>>>>> +  clocks:
>>>>>>> +    maxItems: 1
>>>>>>> +    description: Reference to the sensor input clock
>>>>>>> +
>>>>>>> +  clock-names:
>>>>>>> +    maxItems: 1
>>>>>>> +    items:
>>>>>>> +      - const: inck
>>>>>>> +
>>>>>>> +  vana-supply:
>>>>>>> +    description:
>>>>>>> +      Analog voltage supply, 2.8 volts
>>>>>>> +
>>>>>>> +  vdig-supply:
>>>>>>> +    description:
>>>>>>> +      Digital IO voltage supply, 1.8 volts
>>>>>>> +
>>>>>>> +  vddl-supply:
>>>>>>> +    description:
>>>>>>> +      Digital core voltage supply, 1.2 volts
>>>>>> 4ea3273d24b introduced these regulators as VANA-supply, VDIG-supply
>>>>>> and VDDL-supply (please note the upper-case names). This version uses
>>>>>> lower-case ones instead. Is this intentional ? The driver currently
>>>>>> does not parse any of these if I'm not mistaken, but as the bindings
>>>>>> in textual form defines an ABI which should be preserved during the
>>>>>> conversion to json-schema, should these be kept in upper-case ?
>>>>>>
>>>>>> Thanks
>>>>>>       j
>>>>> Yes, based on feedback lower case was recommended. So, changed to use
>>>>> lower-case names.
>>>>>
>>>>> These properties were not used by driver currently and from my prior series
>>>>> only dt-binding got merged as  no feedback was received on it for all prior
>>>>> versions.
>>>>>
>>>>> So, should be ok to change to lower-case as there properties are introduced
>>>>> now and driver update using these properties is under review
>>>>>
>>>> Well, I see that patch went in v5.9-rc1, so it will be part of v5.9.
>>>>
>>>> If the bindings update goes in in v5.10 (or whatever comes after v5.9)
>>>> then we have a problem, as the DTB created for v5.9 won't work anymore
>>>> on any later version, and that should not happen. Alternatively, a fix
>>>> for the next -rc release could be fast-tracked, but you would
>>>> need to synchronize with the dt maintainers for that and make a patch
>>>> for the existing .txt bindings file.
>>>>
>>>> If the name change happens in the yaml file and one release is made
>>>> with the old names, then we're stuck with those forever and ever, if I
>>>> got the situation right.
>>>>
>>>> Please check with the dt and media maintainers, or they can comment
>>>> here if they glance through these lines.
>>>>
>>>> Thanks
>>>>     j
>>> Hi Leon Luo,
>>>
>>> I used upper case for regulator supply names in all prior 4 versions of
>>> IMX274 patch series as I see some other media i2c drivers doing it and
>>> dt-binding patch from v3 got merged in 5.9-rc1 which was using upper-case.
>>>
>>> Later received feedback from Sakari requesting to use lower-case names so
>>> updated to use lower case name now in v5.
>>>
>>> Not sure if we have timeline to squeeze in patch to change names to
>>> lower-case before they get into 5.10.
>>>
>>> Can you please comment?
>> We can merge patches through the fixes branch if needed. That is not an
>> issue.
>>
> Good! So I'll make a v5 of the json-schema bindings soon that includes
> the lower-case supplies and clock names and let's merge it as a fix in
> this release cycle.
>
> Sowjanya is this ok with you ?
Yes fine for me.
> Sakari, I'll then trust you to fast-track the patch if no other
> issues!
>
> Thanks
>    j
>
>>> Sakari,
>>>
>>> Can you also help understand why can't we keep upper case for regulator
>>> supplies?
>>>
>>> I see some other media i2c drivers using upper case as well.
>> The vast majority of bindings use lower case, that's it, simply.
>>
>> --
>> Regards,
>>
>> Sakari Ailus

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