linux-kernel - Re: [PATCH] hwmon: ntc_thermistor: Add ntc thermistor to thermal subsystem as a sensor.

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Message-id: <53FC5D7B.4040506@samsung.com>
Date:	Tue, 26 Aug 2014 19:12:11 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Jonghwa Lee <jonghwa3.lee@...sung.com>
Cc:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	jdelvare@...e.de, linux@...ck-us.net
Subject: Re: [PATCH] hwmon: ntc_thermistor: Add ntc thermistor to thermal
 subsystem as a sensor.

Hi Jonghwa,

On 08/26/2014 02:33 PM, Jonghwa Lee wrote:
> To get more comprehensive and integrated thermal management, it adds ntc
> thermistor to thermal framework as a thermal sensor. It's governed thermal
> susbsystem only if it is described in DT node. Otherwise, it just notifies
> temperature to userspace via sysfs as it used to be.
> 
> Signed-off-by: Jonghwa Lee <jonghwa3.lee@...sung.com>
> ---
>  .../devicetree/bindings/hwmon/ntc_thermistor.txt   |    3 +++
>  drivers/hwmon/ntc_thermistor.c                     |   26 ++++++++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt b/Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt
> index 2391e5c..fcca8e7 100644
> --- a/Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt
> +++ b/Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt
> @@ -25,6 +25,9 @@ Requires node properties:
>  - "io-channels"	Channel node of ADC to be used for
>  		conversion.
>  
> +Optional node properties:
> +- "#thermal-sensor-cells" Used to expose itself to thermal fw.
> +
>  Read more about iio bindings at
>  	Documentation/devicetree/bindings/iio/iio-bindings.txt
>  
> diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
> index bd41072..369dc8c 100644
> --- a/drivers/hwmon/ntc_thermistor.c
> +++ b/drivers/hwmon/ntc_thermistor.c
> @@ -38,6 +38,7 @@
>  
>  #include <linux/hwmon.h>
>  #include <linux/hwmon-sysfs.h>
> +#include <linux/thermal.h>
>  
>  struct ntc_compensation {
>  	int		temp_c;
> @@ -182,6 +183,7 @@ struct ntc_data {
>  	struct device *dev;
>  	int n_comp;
>  	char name[PLATFORM_NAME_SIZE];
> +	struct thermal_zone_device *tz;
>  };
>  
>  #if defined(CONFIG_OF) && IS_ENABLED(CONFIG_IIO)
> @@ -428,6 +430,20 @@ static int ntc_thermistor_get_ohm(struct ntc_data *data)
>  	return -EINVAL;
>  }
>  
> +static int ntc_read_temp(void *dev, long *temp)
> +{
> +	struct ntc_data *data = dev_get_drvdata(dev);
> +	int ohm;
> +
> +	ohm = ntc_thermistor_get_ohm(data);
> +	if (ohm < 0)
> +		return ohm;
> +
> +	*temp = get_temp_mc(data, ohm);
> +
> +	return 0;
> +}
> +
>  static ssize_t ntc_show_name(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> @@ -562,6 +578,13 @@ static int ntc_thermistor_probe(struct platform_device *pdev)
>  	dev_info(&pdev->dev, "Thermistor type: %s successfully probed.\n",
>  								pdev_id->name);
>  
> +	data->tz = thermal_zone_of_sensor_register(data->dev, 0, data->dev,
> +						ntc_read_temp, NULL);
> +	if (IS_ERR(data->tz)) {
> +		dev_dbg(&pdev->dev, "Failed to register to thermal fw.\n");
> +		data->tz = NULL;
> +	}
> +
>  	return 0;
>  err_after_sysfs:
>  	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
> @@ -578,6 +601,9 @@ static int ntc_thermistor_remove(struct platform_device *pdev)
>  	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
>  	ntc_iio_channel_release(pdata);
>  
> +	if (data->tz)
> +		thermal_zone_of_sensor_unregister(data->dev, data->tz);

thermal_zone_of_sensor_unregister just return without operation if data->tz is NULL.
So, don't need to check the value of data->tz with if statement.

Thanks,
Chanwoo Choi
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