Commit 8c14d126 authored by Chris Verges's avatar Chris Verges Committed by Guenter Roeck
Browse files

hwmon: (lm73) Add 'update_interval' attribute 



The LM73 supports four A/D conversion resolutions.  The default used by
the existing lm73 driver is the chip's default, 11-bit (0.25 C/LSB).
This patch enables changing of this resolution from userspace via the
update_interval sysfs attribute.  Full details on usage are included in
Documentation/hwmon/lm73.

Signed-off-by: default avatarChris Verges <kg4ysn@gmail.com>
[linux@roeck-us.net: cleanup]
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 91bba688

Documentation/hwmon/lm73

0 → 100644
+79 −0
Original line number Diff line number Diff line 
Kernel driver lm73

==================



Supported chips:

  * Texas Instruments LM73

    Prefix: 'lm73'

    Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e

    Datasheet: Publicly available at the Texas Instruments website

               http://www.ti.com/product/lm73



Author: Guillaume Ligneul <guillaume.ligneul@gmail.com>

Documentation: Chris Verges <kg4ysn@gmail.com>





Description

-----------



The LM73 is a digital temperature sensor.  All temperature values are

given in degrees Celsius.



Measurement Resolution Support

------------------------------



The LM73 supports four resolutions, defined in terms of degrees C per

LSB: 0.25, 0.125, 0.0625, and 0.3125.  Changing the resolution mode

affects the conversion time of the LM73's analog-to-digital converter.

From userspace, the desired resolution can be specified as a function of

conversion time via the 'update_interval' sysfs attribute for the

device.  This attribute will normalize ranges of input values to the

maximum times defined for the resolution in the datasheet.



    Resolution    Conv. Time    Input Range

    (C/LSB)       (msec)        (msec)

    --------------------------------------

    0.25          14             0..14

    0.125         28            15..28

    0.0625        56            29..56

    0.03125       112           57..infinity

    --------------------------------------



The following examples show how the 'update_interval' attribute can be

used to change the conversion time:



    $ echo 0 > update_interval

    $ cat update_interval

    14

    $ cat temp1_input

    24250



    $ echo 22 > update_interval

    $ cat update_interval

    28

    $ cat temp1_input

    24125



    $ echo 56 > update_interval

    $ cat update_interval

    56

    $ cat temp1_input

    24062



    $ echo 85 > update_interval

    $ cat update_interval

    112

    $ cat temp1_input

    24031



As shown here, the lm73 driver automatically adjusts any user input for

'update_interval' via a step function.  Reading back the

'update_interval' value after a write operation will confirm the

conversion time actively in use.



Mathematically, the resolution can be derived from the conversion time

via the following function:



   g(x) = 0.250 * [log(x/14) / log(2)]



where 'x' is the output from 'update_interval' and 'g(x)' is the

resolution in degrees C per LSB.

drivers/hwmon/lm73.c

+86 −11
Original line number Diff line number Diff line
@@ -39,8 +39,24 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, 
#define LM73_TEMP_MIN		(-256000 / 250)

#define LM73_TEMP_MAX		(255750 / 250)



/*-----------------------------------------------------------------------*/

#define LM73_CTRL_RES_SHIFT	5

#define LM73_CTRL_RES_MASK	(BIT(5) | BIT(6))

#define LM73_CTRL_TO_MASK	BIT(7)



static const unsigned short lm73_convrates[] = {

	14,	/* 11-bits (0.25000 C/LSB): RES1 Bit = 0, RES0 Bit = 0 */

	28,	/* 12-bits (0.12500 C/LSB): RES1 Bit = 0, RES0 Bit = 1 */

	56,	/* 13-bits (0.06250 C/LSB): RES1 Bit = 1, RES0 Bit = 0 */

	112,	/* 14-bits (0.03125 C/LSB): RES1 Bit = 1, RES0 Bit = 1 */

};



struct lm73_data {

	struct device *hwmon_dev;

	struct mutex lock;

	u8 ctrl;			/* control register value */

};



/*-----------------------------------------------------------------------*/



static ssize_t set_temp(struct device *dev, struct device_attribute *da,

			const char *buf, size_t count)
@@ -78,6 +94,51 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *da, 
	return scnprintf(buf, PAGE_SIZE, "%d\n", temp);

}



static ssize_t set_convrate(struct device *dev, struct device_attribute *da,

			    const char *buf, size_t count)

{

	struct i2c_client *client = to_i2c_client(dev);

	struct lm73_data *data = i2c_get_clientdata(client);

	unsigned long convrate;

	s32 err;

	int res = 0;



	err = kstrtoul(buf, 10, &convrate);

	if (err < 0)

		return err;



	/*

	 * Convert the desired conversion rate into register bits.

	 * res is already initialized, and everything past the second-to-last

	 * value in the array is treated as belonging to the last value

	 * in the array.

	 */

	while (res < (ARRAY_SIZE(lm73_convrates) - 1) &&

			convrate > lm73_convrates[res])

		res++;



	mutex_lock(&data->lock);

	data->ctrl &= LM73_CTRL_TO_MASK;

	data->ctrl |= res << LM73_CTRL_RES_SHIFT;

	err = i2c_smbus_write_byte_data(client, LM73_REG_CTRL, data->ctrl);

	mutex_unlock(&data->lock);



	if (err < 0)

		return err;



	return count;

}



static ssize_t show_convrate(struct device *dev, struct device_attribute *da,

			     char *buf)

{

	struct i2c_client *client = to_i2c_client(dev);

	struct lm73_data *data = i2c_get_clientdata(client);

	int res;



	res = (data->ctrl & LM73_CTRL_RES_MASK) >> LM73_CTRL_RES_SHIFT;

	return scnprintf(buf, PAGE_SIZE, "%hu\n", lm73_convrates[res]);

}



/*-----------------------------------------------------------------------*/
@@ -89,13 +150,14 @@ static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, 
			show_temp, set_temp, LM73_REG_MIN);

static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,

			show_temp, NULL, LM73_REG_INPUT);



static SENSOR_DEVICE_ATTR(update_interval, S_IWUSR | S_IRUGO,

			show_convrate, set_convrate, 0);



static struct attribute *lm73_attributes[] = {

	&sensor_dev_attr_temp1_input.dev_attr.attr,

	&sensor_dev_attr_temp1_max.dev_attr.attr,

	&sensor_dev_attr_temp1_min.dev_attr.attr,



	&sensor_dev_attr_update_interval.dev_attr.attr,

	NULL

};
@@ -110,23 +172,36 @@ static const struct attribute_group lm73_group = { 
static int

lm73_probe(struct i2c_client *client, const struct i2c_device_id *id)

{

	struct device *hwmon_dev;

	int status;

	struct lm73_data *data;

	int ctrl;



	data = devm_kzalloc(&client->dev, sizeof(struct lm73_data),

			    GFP_KERNEL);

	if (!data)

		return -ENOMEM;



	i2c_set_clientdata(client, data);

	mutex_init(&data->lock);



	ctrl = i2c_smbus_read_byte_data(client, LM73_REG_CTRL);

	if (ctrl < 0)

		return ctrl;

	data->ctrl = ctrl;



	/* Register sysfs hooks */

	status = sysfs_create_group(&client->dev.kobj, &lm73_group);

	if (status)

		return status;



	hwmon_dev = hwmon_device_register(&client->dev);

	if (IS_ERR(hwmon_dev)) {

		status = PTR_ERR(hwmon_dev);

	data->hwmon_dev = hwmon_device_register(&client->dev);

	if (IS_ERR(data->hwmon_dev)) {

		status = PTR_ERR(data->hwmon_dev);

		goto exit_remove;

	}

	i2c_set_clientdata(client, hwmon_dev);



	dev_info(&client->dev, "%s: sensor '%s'\n",

		 dev_name(hwmon_dev), client->name);

		 dev_name(data->hwmon_dev), client->name);



	return 0;
@@ -137,9 +212,9 @@ exit_remove: 


static int lm73_remove(struct i2c_client *client)

{

	struct device *hwmon_dev = i2c_get_clientdata(client);

	struct lm73_data *data = i2c_get_clientdata(client);



	hwmon_device_unregister(hwmon_dev);

	hwmon_device_unregister(data->hwmon_dev);

	sysfs_remove_group(&client->dev.kobj, &lm73_group);

	return 0;

}

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