linux-kernel - Re: [PATCH v1 1/1] hwmon: (pmbus) Add regulator supply into macro

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Message-ID: <f76951929710e6f71e59c5ed10767a5f983db943.camel@sylv.io>
Date:   Mon, 21 Feb 2022 11:59:41 +0100
From:   sylv <sylv@...v.io>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>
Subject: Re: [PATCH v1 1/1] hwmon: (pmbus) Add regulator supply into macro

On Thu, 2022-02-17 at 18:40 +0100, sylv wrote:
> On Thu, 2022-02-17 at 09:36 -0800, Guenter Roeck wrote:
> > On 2/17/22 02:23, Marcello Sylvester Bauer wrote:
> > > Add optional regulator supply into PWBUS_REGULATOR macro. This
> > > makes it
> > 
> > The code doesn't look optional to me. What exactly is optional ?
> 
> I mean, it is optional to add a supply. It should not cause errors if
> you don't. I should probably reword this, too.
> 
> > 
> > > possible to define a vin-supply in DT. Not defining a supply will
> > > only
> > > cause the following debug output:
> > > 
> > > ```
> > > Looking up vin-supply property in node [...] failed
> > > ```
> > > 
> > > Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>
> > > ---
> > >   drivers/hwmon/pmbus/pmbus.h | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/hwmon/pmbus/pmbus.h
> > > b/drivers/hwmon/pmbus/pmbus.h
> > > index e0aa8aa46d8c..38f049d68d32 100644
> > > --- a/drivers/hwmon/pmbus/pmbus.h
> > > +++ b/drivers/hwmon/pmbus/pmbus.h
> > > @@ -464,6 +464,7 @@ extern const struct regulator_ops
> > > pmbus_regulator_ops;
> > >   #define PMBUS_REGULATOR(_name, _id)                           \
> > >         [_id] = {                                               \
> > >                 .name = (_name # _id),                          \
> > > +               .supply_name = "vin",                           \
> > >                 .id = (_id),                                    \
> > >                 .of_match = of_match_ptr(_name # _id),          \
> > >                 .regulators_node = of_match_ptr("regulators"),  \
> > 
> > That seems to be quite far reaching. How does this affect / change
> > behavior
> > of existing systems which so far did not expect supply_name to be
> > set
> > ?
> > 
> > Guenter
> 


My goal is to make it optional to define a supply regulator so that it
is possible to regulate the incoming voltage regulator.
IIUIC, it is required to set a supply_name to tell the regulator core
which supply it should look up from DT. (see: of_get_regulator 
drivers/regulator/core.c:402)
This should not cause a change of behavior even if no supply is
defined. It would register a dummy regulator as supply instead.

Am I right, or did I misunderstanding something?

Thanks,
Marcello