diff options
| -rw-r--r-- | Documentation/hwmon/ds1621 | 65 | ||||
| -rw-r--r-- | drivers/hwmon/ds1621.c | 56 |
2 files changed, 121 insertions, 0 deletions
diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621 index d66f76f9d85d..b61e77c6b1cb 100644 --- a/Documentation/hwmon/ds1621 +++ b/Documentation/hwmon/ds1621 @@ -75,3 +75,68 @@ The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0 degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm default setting of 75 and 80 degrees respectively, and a maximum conversion time of 750ms. + +In addition, the DS1721 supports four resolution settings from 9 to 12 bits +(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectifully), +that are set at device power on to the highest resolution: 12-bits (0.0625 degree C). + +Changing the DS1721 resolution mode affects the conversion time and can be +done from userspace, via the device 'update_interval' sysfs attribute. This +attribute will normalize range of input values to the device maximum resolution +values defined in the datasheet as such: + +Resolution Conversion Time Input Range + (C/LSB) (msec) (msec) +-------------------------------------------- +0.5 93.75 0....94 +0.25 187.5 95...187 +0.125 375 188..375 +0.0625 750 376..infinity +-------------------------------------- + +The following examples show how the 'update_interval' attribute can be +used to change the conversion time: + +$ cat update_interval +750 +$ cat temp1_input +22062 +$ +$ echo 300 > update_interval +$ cat update_interval +375 +$ cat temp1_input +22125 +$ +$ echo 150 > update_interval +$ cat update_interval +188 +$ cat temp1_input +22250 +$ +$ echo 1 > update_interval +$ cat update_interval +94 +$ cat temp1_input +22000 +$ +$ echo 1000 > update_interval +$ cat update_interval +750 +$ cat temp1_input +22062 +$ + +As shown, the ds1621 driver automatically adjusts the 'update_interval' +user input, via a step function. Reading back the 'update_interval' value +after a write operation provides the conversion time used by the device. + +Mathematically, the resolution can be derived from the conversion time +via the following function: + + g(x) = 0.5 * [minimum_conversion_time/x] + +where: + -> 'x' = the output from 'update_interval' + -> 'g(x)' = the resolution in degrees C per LSB. + -> 93.75ms = minimum conversion time diff --git a/drivers/hwmon/ds1621.c b/drivers/hwmon/ds1621.c index 6942617666a4..b5d80fb851d0 100644 --- a/drivers/hwmon/ds1621.c +++ b/drivers/hwmon/ds1621.c @@ -274,7 +274,47 @@ static ssize_t show_alarm(struct device *dev, struct device_attribute *da, return sprintf(buf, "%d\n", !!(data->conf & attr->index)); } +static ssize_t show_convrate(struct device *dev, struct device_attribute *da, + char *buf) +{ + struct i2c_client *client = to_i2c_client(dev); + struct ds1621_data *data = i2c_get_clientdata(client); + return scnprintf(buf, PAGE_SIZE, "%hu\n", data->update_interval); +} + +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 ds1621_data *data = i2c_get_clientdata(client); + unsigned long convrate; + s32 err; + int resol = 0; + + err = kstrtoul(buf, 10, &convrate); + if (err) + return err; + + /* Convert rate into resolution bits */ + while (resol < (ARRAY_SIZE(ds1721_convrates) - 1) && + convrate > ds1721_convrates[resol]) + resol++; + + mutex_lock(&data->update_lock); + data->conf = i2c_smbus_read_byte_data(client, DS1621_REG_CONF); + data->conf &= ~DS1621_REG_CONFIG_RESOL; + data->conf |= (resol << DS1621_REG_CONFIG_RESOL_SHIFT); + i2c_smbus_write_byte_data(client, DS1621_REG_CONF, data->conf); + data->update_interval = ds1721_convrates[resol]; + mutex_unlock(&data->update_lock); + + return count; +} + static DEVICE_ATTR(alarms, S_IRUGO, show_alarms, NULL); +static DEVICE_ATTR(update_interval, S_IWUSR | S_IRUGO, show_convrate, + set_convrate); + static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL, 0); static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, show_temp, set_temp, 1); static SENSOR_DEVICE_ATTR(temp1_max, S_IWUSR | S_IRUGO, show_temp, set_temp, 2); @@ -290,11 +330,27 @@ static struct attribute *ds1621_attributes[] = { &sensor_dev_attr_temp1_min_alarm.dev_attr.attr, &sensor_dev_attr_temp1_max_alarm.dev_attr.attr, &dev_attr_alarms.attr, + &dev_attr_update_interval.attr, NULL }; +static umode_t ds1621_attribute_visible(struct kobject *kobj, + struct attribute *attr, int index) +{ + struct device *dev = container_of(kobj, struct device, kobj); + struct i2c_client *client = to_i2c_client(dev); + struct ds1621_data *data = i2c_get_clientdata(client); + + if (attr == &dev_attr_update_interval.attr) + if (data->kind != ds1721) + /* shhh, we're hiding update_interval */ + return 0; + return attr->mode; +} + static const struct attribute_group ds1621_group = { .attrs = ds1621_attributes, + .is_visible = ds1621_attribute_visible }; |