hwmon: (lm75) Prepare to support per-chip resolution and sample time

Prepare the lm75 driver to support per-chip resolution and sample
time. For now we only make the code generic enough to support it, but
we still use the same, unchanged resolution (9-bit) and sample time
(1.5 s) for all chips.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Acked-by: NGuenter Roeck <linux@roeck-us.net>

drivers/hwmon/lm75.c

@@ -71,9 +71,12 @@ struct lm75_data {
 	struct device		*hwmon_dev;
 	struct mutex		update_lock;
 	u8			orig_conf;
+	u8			resolution;	/* In bits, between 9 and 12 */
+	u8			resolution_limits;
 	char			valid;		/* !=0 if registers are valid */
 	unsigned long		last_updated;	/* In jiffies */
-	u16			temp[3];	/* Register values,
+	unsigned long		sample_time;	/* In jiffies */
+	s16			temp[3];	/* Register values,
 						   0 = input
 						   1 = max
 						   2 = hyst */
@@ -93,12 +96,15 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *da,
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	struct lm75_data *data = lm75_update_device(dev);
+	long temp;
 
 	if (IS_ERR(data))
 		return PTR_ERR(data);
 
-	return sprintf(buf, "%d\n",
-		       LM75_TEMP_FROM_REG(data->temp[attr->index]));
+	temp = ((data->temp[attr->index] >> (16 - data->resolution)) * 1000)
+	       >> (data->resolution - 8);
+
+	return sprintf(buf, "%ld\n", temp);
 }
 
 static ssize_t set_temp(struct device *dev, struct device_attribute *da,
@@ -110,13 +116,25 @@ static ssize_t set_temp(struct device *dev, struct device_attribute *da,
 	int nr = attr->index;
 	long temp;
 	int error;
+	u8 resolution;
 
 	error = kstrtol(buf, 10, &temp);
 	if (error)
 		return error;
 
+	/*
+	 * Resolution of limit registers is assumed to be the same as the
+	 * temperature input register resolution unless given explicitly.
+	 */
+	if (attr->index && data->resolution_limits)
+		resolution = data->resolution_limits;
+	else
+		resolution = data->resolution;
+
 	mutex_lock(&data->update_lock);
-	data->temp[nr] = LM75_TEMP_TO_REG(temp);
+	temp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
+	data->temp[nr] = DIV_ROUND_CLOSEST(temp  << (resolution - 8),
+					   1000) << (16 - resolution);
 	lm75_write_value(client, LM75_REG_TEMP[nr], data->temp[nr]);
 	mutex_unlock(&data->update_lock);
 	return count;
@@ -190,6 +208,9 @@ lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		break;
 	}
 
+	data->resolution = 9;
+	data->sample_time = HZ + HZ / 2;
+
 	/* configure as specified */
 	status = lm75_read_value(client, LM75_REG_CONF);
 	if (status < 0) {
@@ -427,7 +448,7 @@ static struct lm75_data *lm75_update_device(struct device *dev)
 
 	mutex_lock(&data->update_lock);
 
-	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
+	if (time_after(jiffies, data->last_updated + data->sample_time)
 	    || !data->valid) {
 		int i;
 		dev_dbg(&client->dev, "Starting lm75 update\n");