Re: [RFC PATCH 03/14] hwmon: lm75: expose to thermal fw via DT nodes

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Aug 23, 2013 at 07:15:44PM -0400, Eduardo Valentin wrote:
> This patch adds to lm75 temperature sensor the possibility
> to expose itself as thermal zone device, registered on the
> thermal framework.
> 
> The thermal zone is built only if a device tree node
> describing a thermal zone for this sensor is present
> inside the lm75 DT node. Otherwise, the driver behavior
> will be the same.
> 
> Cc: Jean Delvare <khali@linux-fr.org>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: lm-sensors@lm-sensors.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
> ---
>  drivers/hwmon/lm75.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
> index c03b490..dc55908 100644
> --- a/drivers/hwmon/lm75.c
> +++ b/drivers/hwmon/lm75.c
> @@ -27,6 +27,8 @@
>  #include <linux/hwmon-sysfs.h>
>  #include <linux/err.h>
>  #include <linux/mutex.h>
> +#include <linux/thermal.h>
> +#include <linux/of.h>
>  #include "lm75.h"
>  
>  
> @@ -70,6 +72,7 @@ static const u8 LM75_REG_TEMP[3] = {
>  /* Each client has this additional data */
>  struct lm75_data {
>  	struct device		*hwmon_dev;
> +	struct thermal_zone_device	*tz;
>  	struct mutex		update_lock;
>  	u8			orig_conf;
>  	u8			resolution;	/* In bits, between 9 and 12 */
> @@ -92,6 +95,19 @@ static struct lm75_data *lm75_update_device(struct device *dev);
>  
>  /* sysfs attributes for hwmon */
>  
> +static int lm75_read_temp(void *dev, unsigned long *temp)
> +{
> +	struct lm75_data *data = lm75_update_device(dev);
> +
> +	if (IS_ERR(data))
> +		return PTR_ERR(data);
> +
> +	*temp = ((data->temp[0] >> (16 - data->resolution)) * 1000) >>
> +			(data->resolution - 8);
> +
The reported temperature can be negative, which would result in reporting a very
high temperature (note this applies to the tmp102 driver patch as well).

The computation is quite complex and matches the computation done in show_temp().
Given that, it would make sense to declare an inline function to convert the
register value to the temperature. This function can take the register value
and the resolution as argument.

Guenter

> +	return 0;
> +}
> +
>  static ssize_t show_temp(struct device *dev, struct device_attribute *da,
>  			 char *buf)
>  {
> @@ -271,11 +287,25 @@ lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
>  		goto exit_remove;
>  	}
>  
> +	if (of_find_property(client->dev.of_node, "monitored-zones", NULL)) {
> +		data->tz = thermal_zone_of_device_register(&client->dev,
> +							   0,
> +							   false, /* -hwmon */
> +							   &client->dev,
> +							   lm75_read_temp);
> +		if (IS_ERR(data->tz)) {
> +			status = PTR_ERR(data->tz);
> +			goto exit_hwmon;
> +		}
> +	}
> +
>  	dev_info(&client->dev, "%s: sensor '%s'\n",
>  		 dev_name(data->hwmon_dev), client->name);
>  
>  	return 0;
>  
> +exit_hwmon:
> +	hwmon_device_unregister(data->hwmon_dev);
>  exit_remove:
>  	sysfs_remove_group(&client->dev.kobj, &lm75_group);
>  	return status;
> @@ -285,6 +315,7 @@ static int lm75_remove(struct i2c_client *client)
>  {
>  	struct lm75_data *data = i2c_get_clientdata(client);
>  
> +	thermal_zone_device_unregister(data->tz);
>  	hwmon_device_unregister(data->hwmon_dev);
>  	sysfs_remove_group(&client->dev.kobj, &lm75_group);
>  	lm75_write_value(client, LM75_REG_CONF, data->orig_conf);
> -- 
> 1.8.2.1.342.gfa7285d
> 
>