Make the lm75 driver so that use the best resolution available on
each chip it finds ... usually this is 12 bits (0.0625 degrees C).
Note that this preserves the quirky "round away from zero" behavior
for converting temperatures to sensor values. (I'd think any rounding
should be done after conversion, not before, if it's even done.)
Signed-off-by: David Brownell <dbrownell at users.sourceforge.net>
---
drivers/hwmon/Kconfig | 4 +++-
drivers/hwmon/lm75.c | 44 ++++++++++++++++++++++++++++++++++++--------
2 files changed, 39 insertions(+), 9 deletions(-)
--- a/drivers/hwmon/Kconfig 2007-09-27 13:50:47.000000000 -0700
+++ b/drivers/hwmon/Kconfig 2007-09-27 14:36:36.000000000 -0700
@@ -313,7 +313,9 @@ config SENSORS_LM75
- Texas Instruments TMP100, TMP101, TMP75, TMP175, TMP275
This driver supports driver model based binding through board
- specific I2C device tables.
+ specific I2C device tables. When those tables report a chip
+ type that's recognized as supporting it, this driver uses 12-bit
+ sample resolution (to 1/16 degree C).
It also supports the "legacy" style of driver binding. To use
that with some chips which don't replicate LM75 quirks exactly,
--- a/drivers/hwmon/lm75.c 2007-09-27 14:26:44.000000000 -0700
+++ b/drivers/hwmon/lm75.c 2007-09-27 16:07:49.000000000 -0700
@@ -27,7 +27,6 @@
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.h>
-#include "lm75.h"
/*
@@ -65,6 +64,8 @@ struct lm75_data {
0 = input
1 = max
2 = hyst */
+ u16 round; /* f(resolution) */
+ u16 mask;
};
static int lm75_read_value(struct i2c_client *client, u8 reg);
@@ -74,7 +75,7 @@ static struct lm75_data *lm75_update_dev
/*-----------------------------------------------------------------------*/
-/* sysfs attributes for hwmon */
+/* sysfs attributes for hwmon, handling any sample resolution */
static inline s16 temp_to_reg(struct lm75_data *lm75, long temp)
{
@@ -83,12 +84,19 @@ static inline s16 temp_to_reg(struct lm7
else if (temp > lm75->max)
temp = lm75->max;
- return LM75_TEMP_TO_REG(temp);
+ /* "Round away from zero" -- unusual but backwards-compatible.
+ * Rounding should really be done *after* conversion.
+ */
+ temp += (temp < 0) ? -lm75->round : lm75->round;
+ return ((temp * 256) / 1000) & lm75->mask;
}
static inline int reg_to_temp(s16 reg)
{
- return LM75_TEMP_FROM_REG(reg);
+ /* Use integer division instead of logical right shift to
+ * preserve sign (compiler uses arithmetic right shift).
+ */
+ return (reg * 1000) / 256;
}
static ssize_t show_temp(struct device *dev, struct device_attribute *da,
@@ -97,7 +105,8 @@ static ssize_t show_temp(struct device *
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
struct lm75_data *data = lm75_update_device(dev);
- return sprintf(buf, "%d\n", reg_to_temp(data->temp[attr->index]));
+ return sprintf(buf, "%d\n",
+ reg_to_temp(data->temp[attr->index]) & data->mask);
}
static ssize_t set_temp(struct device *dev, struct device_attribute *da,
@@ -144,6 +153,7 @@ static int lm75_probe(struct i2c_client
int status;
u8 set_mask, clr_mask;
int new;
+ int resolution;
if (!i2c_check_functionality(client->adapter,
I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
@@ -163,13 +173,27 @@ static int lm75_probe(struct i2c_client
set_mask = 0;
clr_mask = (1 << 0) /* continuous conversions */
| (1 << 6) | (1 << 5); /* 9-bit mode */
+ resolution = 9;
data->min = -55 * 1000;
data->max = 125 * 1000;
/* for tmp175 or tmp275, use name "tmp75" */
- if (strcmp(client->name, "tmp75") == 0)
+ if (strcmp(client->name, "tmp75") == 0) {
data->min = -40 * 1000;
+ set_mask |= (1 << 6) | (1 << 5);
+ resolution = 12;
+
+ /* for ds1775, use name "ds75" */
+ } else if (strcmp(client->name, "ds75") == 0
+ || strcmp(client->name, "mcp980x") == 0
+ || strcmp(client->name, "tmp100") == 0
+ || strcmp(client->name, "tmp101") == 0) {
+ set_mask |= (1 << 6) | (1 << 5);
+ resolution = 12;
+
+ } else if (strcmp(client->name, "max6626") == 0)
+ resolution = 12;
/* NOTE: also need to ensure that the chip is in interrupt mode
* in various cases, and maybe handle SMBALERT#.
@@ -188,6 +212,9 @@ static int lm75_probe(struct i2c_client
lm75_write_value(client, LM75_REG_CONF, new);
dev_dbg(&client->dev, "Config %02x\n", new);
+ data->round = 500 / (1 << (resolution - 8));
+ data->mask = ~((1 << (16 - resolution)) - 1);
+
/* Register sysfs hooks */
if ((status = sysfs_create_group(&client->dev.kobj, &lm75_group)))
goto exit_free;
@@ -198,8 +225,9 @@ static int lm75_probe(struct i2c_client
goto exit_remove;
}
- dev_info(&client->dev, "%s: sensor '%s'\n",
- data->hwmon_dev->bus_id, client->name);
+ dev_info(&client->dev,
+ "%s: sensor '%s', resolution %d millidegrees C\n",
+ data->hwmon_dev->bus_id, client->name, data->round * 2);
return 0;
