Re: [PATCH] hwmon: (ina2xx) make regulator 'vs' support optional

[Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>]

On 4/3/2025 7:06 PM, Guenter Roeck wrote:
> On Thu, Apr 03, 2025 at 05:29:26PM +0300, Ciprian Marian Costea wrote:
>> On 4/3/2025 3:15 PM, Guenter Roeck wrote:
>>> On 4/3/25 03:15, Ciprian Costea wrote:
>>>> From: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
>>>>
>>>> S32G2/S32G3 based boards which integrate the ina231 sensor do not have a
>>>> dedicated voltage regulator.
>>>>
>>>> Co-developed-by: Florin Buica <florin.buica@nxp.com>
>>>> Signed-off-by: Florin Buica <florin.buica@nxp.com>
>>>> Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
>>>> ---
>>>>    drivers/hwmon/ina2xx.c | 4 ++--
>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
>>>> index 345fe7db9de9..ab4972f94a8c 100644
>>>> --- a/drivers/hwmon/ina2xx.c
>>>> +++ b/drivers/hwmon/ina2xx.c
>>>> @@ -959,8 +959,8 @@ static int ina2xx_probe(struct i2c_client *client)
>>>>            return PTR_ERR(data->regmap);
>>>>        }
>>>> -    ret = (dev, "vs");
>>>> -    if (ret)
>>>> +    ret = devm_regulator_get_enable_optional(dev, "vs");
>>>
>>> devm_regulator_get_enable() should provide a dummy regulator if there is
>>> no explicit regulator. Why does this not work ?
>>>
>>>> +    if (ret < 0 && ret != -ENODEV)
>>>
>>> Why this added check ?
>>>
>>> I know it used to be necessary if regulator support is disabled,
>>> but that is no longer the case.
>>>
>>> Guenter
>>>
>>
>> Hello Guenter,
>>
>> I've just tested and devm_regulator_get_enable() does work as you've
>> described, providing a dummy regulator.
>>
>> But, according to the 'ti,ina2xx' binding [1] I see that the `vs-supply`
>> property is not required. Hence wouldn't it be correct for `vs-supply` to be
>> optional ? Using 'devm_regulator_get_enable_optional()'
>>
> Yes, but the reasoning you provided is different and suggested that the
> current code would not work. Since that is not the case, the change would
> be purely cosmetic. Also, I still don't see why the -ENODEV check would be
> necessary.
> 
> Guenter

For boards such as S32G274A-EVB, S32G274A-RDB2 and S32G399A-RDB3 which 
do not have a voltage regulator, 'devm_regulator_get_enable_optional()' 
would return error value -19 (-ENODEV). Also, other usages from the 
Linux Kernel seem to perform the same error check when using 
'devm_regulator_get_enable_optional()' [1], [2] and [3].

This patch would help in S32G2 and S32G3 to not print an unnecessary 
kernel log warning hinting usage of a dummy regulator when such a 
regulator is not required according to the binding.

Would you like me to send a V2 with the commit title updated as follows ?

"
hwmon: (ina2xx) make regulator 'vs' support optional

According to the 'ti,ina2xx' binding, the 'vs-supply' property is 
optional. Furthermore, S32G2/S32G3 based boards which integrate the 
ina231 sensor do not have a dedicated voltage regulator. Thus, making 
regulator support optional would help in avoiding any unnecessary kernel 
log warnings during boot.
"

[1] 
https://elixir.bootlin.com/linux/v6.13.7/source/drivers/iio/adc/ad7625.c#L524-L525
[2] 
https://elixir.bootlin.com/linux/v6.13.7/source/drivers/pci/controller/pcie-rcar-host.c#L982-L983
[3] 
https://elixir.bootlin.com/linux/v6.13.7/source/drivers/iio/adc/ad7944.c#L514-L515

Regards,
Ciprian