linux-kernel - Re: [PATCH] hwmon: (tmp108) Add basic regulator support

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Message-ID: <Z1AZXzw5XnsapWT5@standask-GA-A55M-S2HP>
Date: Wed, 4 Dec 2024 09:57:03 +0100
From: Stanislav Jakubek <stano.jakubek@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org, Frank Li <Frank.Li@....com>
Subject: Re: [PATCH] hwmon: (tmp108) Add basic regulator support

On Sat, Nov 30, 2024 at 09:58:17AM -0800, Guenter Roeck wrote:
> On 11/26/24 00:40, Stanislav Jakubek wrote:
> > TMP108/P3T1085 are powered by the V+/VCC regulator, add support for it.
> > 
> > Signed-off-by: Stanislav Jakubek <stano.jakubek@...il.com>
> > ---
> >   drivers/hwmon/tmp108.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/hwmon/tmp108.c b/drivers/hwmon/tmp108.c
> > index 1f36af2cd2d9..85e4466259a3 100644
> > --- a/drivers/hwmon/tmp108.c
> > +++ b/drivers/hwmon/tmp108.c
> > @@ -17,6 +17,7 @@
> >   #include <linux/init.h>
> >   #include <linux/jiffies.h>
> >   #include <linux/regmap.h>
> > +#include <linux/regulator/consumer.h>
> >   #include <linux/slab.h>
> >   #define	DRIVER_NAME "tmp108"
> > @@ -331,6 +332,10 @@ static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *
> >   	u32 config;
> >   	int err;
> > +	err = devm_regulator_get_enable(dev, "vcc");
> > +	if (err)
> > +		return dev_err_probe(dev, err, "Failed to enable regulator\n");
> > +
> 
> Problem with this is that existing devicetree bindings do not provide
> a reference to the regulator. Those would now fail to instantiate,
> which would be unacceptable. I think you'll need something like

Doesn't devm_regulator_get_enable fallback to a dummy regulator when
a reference to the regulator isn't provided?

lm90 does it this way too.

Regards,
Stanislav

> 
> 	err = devm_regulator_get_enable_optional(dev, "vcc");
> 	if (err && err != -ENODEV)
> 		return dev_err_probe(dev, err, "Failed to enable regulator\n");
> 
> Even though the regulator is now mandatory, existing devicetree bindings
> don't know that.
> 
> Guenter
>