linux-kernel - Re: [PATCH 3/3] hwmon: (lm75) Add regulator support

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Message-ID: <20200928162948.GC106276@roeck-us.net>
Date:   Mon, 28 Sep 2020 09:29:49 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Bedel, Alban" <alban.bedel@...q.com>
Cc:     "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jdelvare@...e.com" <jdelvare@...e.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH 3/3] hwmon: (lm75) Add regulator support

On Mon, Sep 28, 2020 at 03:13:53PM +0000, Bedel, Alban wrote:
> On Thu, 2020-09-17 at 22:33 -0700, Guenter Roeck wrote:
> > On 9/17/20 3:18 AM, Alban Bedel wrote:
> > > Add regulator support for boards where the sensor first need to be
> > > powered up before it can be used.
> > > 
> > > Signed-off-by: Alban Bedel <alban.bedel@...q.com>
> > > ---
> > >  drivers/hwmon/lm75.c | 31 +++++++++++++++++++++++++++++--
> > >  1 file changed, 29 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
> > > index ba0be48aeadd..b673f8d2ef20 100644
> > > --- a/drivers/hwmon/lm75.c
> > > +++ b/drivers/hwmon/lm75.c
> > > @@ -17,6 +17,7 @@
> > >  #include <linux/of.h>
> > >  #include <linux/regmap.h>
> > >  #include <linux/util_macros.h>
> > > +#include <linux/regulator/consumer.h>
> > >  #include "lm75.h"
> > >  
> > >  /*
> > > @@ -101,6 +102,7 @@ static const unsigned short normal_i2c[] = {
> > > 0x48, 0x49, 0x4a, 0x4b, 0x4c,
> > >  struct lm75_data {
> > >  	struct i2c_client		*client;
> > >  	struct regmap			*regmap;
> > > +	struct regulator		*vs;
> > >  	u8				orig_conf;
> > >  	u8				current_conf;
> > >  	u8				resolution;	/* In bits, 9 to 16 */
> > > @@ -540,6 +542,8 @@ static void lm75_remove(void *data)
> > >  	struct i2c_client *client = lm75->client;
> > >  
> > >  	i2c_smbus_write_byte_data(client, LM75_REG_CONF, lm75->orig_conf);
> > > +	if (lm75->vs)
> > > +		regulator_disable(lm75->vs);
> > >  }
> > >  
> > >  static int
> > > @@ -567,6 +571,14 @@ lm75_probe(struct i2c_client *client, const
> > > struct i2c_device_id *id)
> > >  	data->client = client;
> > >  	data->kind = kind;
> > >  
> > > +	data->vs = devm_regulator_get_optional(dev, "vs");
> > 
> > Looking into the regulator API, it may be better if you use
> > devm_regulator_get().
> > AFAICS it returns a dummy regulator if there is none, and NULL if the
> > regulator subsystem is disabled. So
> > 	data->vs = devm_regulator_get(dev, "vs");
> > 	if (IS_ERR(data->vs))
> > 		return PTR_ERR(data->vs);
> > should work and would be less messy.
> 
> Ok, I'll change that in the next version.
> 
> > > +	if (IS_ERR(data->vs)) {
> > > +		if (PTR_ERR(data->vs) == -ENODEV)
> > > +			data->vs = NULL;
> > > +		else
> > > +			return PTR_ERR(data->vs);
> > > +	}
> > > +
> > >  	data->regmap = devm_regmap_init_i2c(client,
> > > &lm75_regmap_config);
> > >  	if (IS_ERR(data->regmap))
> > >  		return PTR_ERR(data->regmap);
> > > @@ -581,11 +593,21 @@ lm75_probe(struct i2c_client *client, const
> > > struct i2c_device_id *id)
> > >  	data->sample_time = data->params->default_sample_time;
> > >  	data->resolution = data->params->default_resolution;
> > >  
> > > +	/* Enable the power */
> > > +	if (data->vs) {
> > > +		err = regulator_enable(data->vs);
> > > +		if (err) {
> > > +			dev_err(dev, "failed to enable regulator:
> > > %d\n", err);
> > > +			return err;
> > > +		}
> > > +	}
> > > +
> > 
> > How about device removal ? Don't you have to call regulator_disable()
> > there as well ? If so, it might be best to use
> > devm_add_action_or_reset() to register a disable function.
> 
> This is handled in lm75_remove() where I added the regulator_disable()
> call.

lm75_remove() won't be called if the probe function fails.

Guenter