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
temp1_update_interval attribute.
To change the resolution, write the maximum conversion time as specified
in the LM73 datasheet for the resolution desired:
echo 14 > temp1_update_interval; # 11-bit, 0.25 C/LSB
echo 28 > temp1_update_interval; # 12-bit, 0.125 C/LSB
echo 56 > temp1_update_interval; # 13-bit, 0.0625 C/LSB
echo 112 > temp1_update_interval; # 14-bit, 0.03125 C/LSB
In essence, the user can trade off conversion time for increased
precision.
Signed-off-by: Chris Verges <kg4ysn@xxxxxxxxx>
---
drivers/hwmon/lm73.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 66 insertions(+), 1 deletion(-)
diff --git a/drivers/hwmon/lm73.c b/drivers/hwmon/lm73.c
index 7272176..e6c1e05 100644
--- a/drivers/hwmon/lm73.c
+++ b/drivers/hwmon/lm73.c
@@ -39,6 +39,17 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c,
#define LM73_TEMP_MIN (-40)
#define LM73_TEMP_MAX 150
+#define LM73_CTRL_RES_OFFSET (5)
+#define LM73_CTRL_RES_SIZE (2)
+#define LM73_CTRL_RES_MASK ((1 << LM73_CTRL_RES_SIZE) - 1)
+
+static long lm73_valid_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 */
+};
+
/*-----------------------------------------------------------------------*/
@@ -79,6 +90,58 @@ 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 sensor_device_attribute *attr = to_sensor_dev_attr(da);
+ struct i2c_client *client = to_i2c_client(dev);
+ long convrate;
+ uint32_t ctrl;
+ u8 res_bits = 0;
+ u8 value;
+ u32 err;
+
+ int status = kstrtol(buf, 10, &convrate);
+ if (status < 0)
+ return status;
+
+ /* Validate the accepted conversion rate */
+ while (res_bits < ARRAY_SIZE(lm73_valid_convrates) && lm73_valid_convrates[res_bits] != convrate)
+ res_bits++;
+
+ if (res_bits >= ARRAY_SIZE(lm73_valid_convrates))
+ return -EINVAL;
+
+ /* Read existing control value */
+ ctrl = i2c_smbus_read_byte_data(client, attr->index);
+ if (ctrl < 0)
+ return ctrl;
+
+ /* Write value */
+ value = ctrl;
+ value &= ~(LM73_CTRL_RES_MASK << LM73_CTRL_RES_OFFSET);
+ value |= ((res_bits & LM73_CTRL_RES_MASK) << LM73_CTRL_RES_OFFSET);
+ err = i2c_smbus_write_byte_data(client, attr->index, value);
+ return (err < 0) ? err : count;
+}
+
+static ssize_t show_convrate(struct device *dev, struct device_attribute *da,
+ char *buf)
+{
+ struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+ struct i2c_client *client = to_i2c_client(dev);
+ uint32_t ctrl;
+ u8 res_bits = 0;
+
+ /* Read existing control value */
+ ctrl = i2c_smbus_read_byte_data(client, attr->index);
+ if (ctrl < 0)
+ return ctrl;
+
+ res_bits = (ctrl & ~LM73_CTRL_RES_MASK) >> LM73_CTRL_RES_OFFSET;
+ return scnprintf(buf, PAGE_SIZE, "%u\n", res_bits);
+}
+
/*-----------------------------------------------------------------------*/
@@ -90,13 +153,15 @@ 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(temp1_update_interval, S_IWUSR | S_IRUGO,
+ show_convrate, set_convrate, LM73_REG_CTRL);
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_temp1_update_interval.dev_attr.attr,
NULL
};
--
1.7.9.5
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