linux-kernel - Re: [PATCH v1 1/2] dt-bindings: hwmon: ina2xx: add supply property

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Message-ID: <2b012916-3955-6c4a-a74b-1e86eaa19485@roeck-us.net>
Date:   Wed, 8 Mar 2023 03:35:46 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Svyatoslav Ryhel <clamor95@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Jean Delvare <jdelvare@...e.com>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-hwmon@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] dt-bindings: hwmon: ina2xx: add supply property

On 3/8/23 02:32, Svyatoslav Ryhel wrote:
> ср, 8 бер. 2023 р. о 12:27 Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> пише:
>>
>> On 08/03/2023 10:40, Svyatoslav Ryhel wrote:
>>> Add supply property.
>>
>> You have entire commit msg to explain and give background, but instead
>> there is just sentence duplicating subject. And since you did not
>> explain anything, we have questions... like: INA238 does not have VDD,
>> so this does not look correct.
>>
> 
> This is why a regulator is not mandatory. If ina238 does not have vdd
> then one who needs ina238 may omit this prop. How about looking from
> this perspective?
> 

If a chip does not have VDD, the driver should not even try to get it
for that chip. INS238 is supported by a different driver, so that does
not require special code, but it needs to be spelled out in the devicetree
bindings. Devicetree has a means to specify if a property is valid for
a given device.

Having said this, as it turns out, _none_ of the chips supported by
the ina2xx and the ina238 drivers have VDD. All of them have Vs, and
all but INA219 have Vbus. The bindings don't even explain which one
of those is supposed to refer to "VDD".

Also, regulator_get_optional() returns -ENODEV if CONFIG_REGULATOR
is not enabled, so it isn't entirely optional. We can not suddenly fail
to load the driver on systems with CONFIG_REGULATOR=n, so some conditional
code will unfortunately be necessary.

Guenter

>>
>> Best regards,
>> Krzysztof
>>
> 
> Best regards,
> Svyatoslav R.