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

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Message-ID: <7986c014-b826-bad1-f19c-cdda31d20804@roeck-us.net>
Date:   Thu, 17 Sep 2020 22:33:37 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alban Bedel <alban.bedel@...q.com>, linux-hwmon@...r.kernel.org
Cc:     Jean Delvare <jdelvare@...e.com>, Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] hwmon: (lm75) Add regulator support

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.

> +	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.

Thanks,
Guenter

>  	/* Cache original configuration */
>  	status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
>  	if (status < 0) {
>  		dev_dbg(dev, "Can't read config? %d\n", status);
> -		return status;
> +		err = status;
> +		goto disable_regulator;
>  	}
>  	data->orig_conf = status;
>  	data->current_conf = status;
> @@ -593,7 +615,7 @@ lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
>  	err = lm75_write_config(data, data->params->set_mask,
>  				data->params->clr_mask);
>  	if (err)
> -		return err;
> +		goto disable_regulator;
>  
>  	err = devm_add_action_or_reset(dev, lm75_remove, data);
>  	if (err)
> @@ -608,6 +630,11 @@ lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
>  	dev_info(dev, "%s: sensor '%s'\n", dev_name(hwmon_dev), client->name);
>  
>  	return 0;
> +
> +disable_regulator:
> +	if (data->vs)
> +		regulator_disable(data->vs);
> +	return err;
>  }
>  
>  static const struct i2c_device_id lm75_ids[] = {
>