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@aerq.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.

Alban