On Mon, Jun 10, 2013 at 01:50:17PM -0700, Robert Coulson wrote:
> The ds1721 device can be configured for 9..12 bit resolutions;
> add a sysfs attribute for userspace to configure this attribute.
> The definition, description, details, and usage are shown in the
> documentation and were crafted from an LM73 driver patch done by
> Chris Verges & Guenter Roeck).
>
> Signed-off-by: Robert Coulson <rob.coulson@xxxxxxxxx>
> ---
>
Appled.
Thanks,
Guenter
> v2 - removes unused devattr variable reported by Jean Delvare.
>
> Documentation/hwmon/ds1621 | 65 ++++++++++++++++++++++++++++++++++++++++++++
> drivers/hwmon/ds1621.c | 56 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 121 insertions(+)
>
> diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621
> index ee7bc01..ae29036 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 Celius over a -10 to +85 degree range, a minimum/maximum alarm
> default setting of 75 and 80 degrees respectifully, 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 04a3b12..763de4c 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
> };
>
>
> --
> 1.7.9.5
>
>
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>
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