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

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Date:	Mon, 26 Aug 2013 08:15:48 -0400
From:	Eduardo Valentin <eduardo.valentin@...com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Eduardo Valentin <eduardo.valentin@...com>,
	<swarren@...dotorg.org>, <pawel.moll@....com>,
	<mark.rutland@....com>, <ian.campbell@...rix.com>,
	<grant.likely@...aro.org>, <rob.herring@...xeda.com>,
	<rui.zhang@...el.com>, <wni@...dia.com>, <durgadoss.r@...el.com>,
	<linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<lm-sensors@...sensors.org>, <linux-kernel@...r.kernel.org>,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: [RFC PATCH 03/14] hwmon: lm75: expose to thermal fw via DT nodes

On 23-08-2013 19:50, Guenter Roeck wrote:
> 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@...ux-fr.org>
>> Cc: Guenter Roeck <linux@...ck-us.net>
>> Cc: lm-sensors@...sensors.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Eduardo Valentin <eduardo.valentin@...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).
> 

Good point.

> 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.

Sounds reasonable. Modifying accordingly in next version.

> 
> 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
>>
>>
> 
> 


-- 
You have got to be excited about what you are doing. (L. Lamport)

Eduardo Valentin


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