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);
> +
> +	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;
> +		}
> +	}
> +
I don't think it should be fatal if thermal_zone_of_device_register fails.
hwmon itself still works fine, and should not be penaltized for a thermal
subsystem failure. Better display a warning if that happens and don't bail out.

The same comment applies to all patches affecting the hwmon subsystem.

>  	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
> 
>