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

[Guenter Roeck]

On 4/4/25 01:36, Ciprian Marian Costea wrote:
> 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@xxxxxxxxxxx>
> > > > >
> > > > > S32G2/S32G3 based boards which integrate the ina231 sensor do not have a
> > > > > dedicated voltage regulator.
> > > > >
> > > > > Co-developed-by: Florin Buica <florin.buica@xxxxxxx>
> > > > > Signed-off-by: Florin Buica <florin.buica@xxxxxxx>
> > > > > Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@xxxxxxxxxxx>
> > > > > ---
> > > > >    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.
> "

Make it:

"According to the 'ti,ina2xx' binding, the 'vs-supply' property is optional.
 Use devm_regulator_get_enable_optional() to avoid a kernel warning message
 if the property is not provided.
"

Then add a note to the code explaining that the check for -ENODEV is necessary
because the regulator core returns -ENODEV if the regulator is not available.

Why it makes sense for this function to return -ENODEV if an _optional_ regulator
is not available escapes me, but that is a different issue.

Guenter