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| author | Jean Delvare <khali@linux-fr.org> | 2009-03-30 21:46:40 +0200 |
|---|---|---|
| committer | Jean Delvare <khali@linux-fr.org> | 2009-03-30 21:46:40 +0200 |
| commit | e4879e28abd67b894fb9d2db0afd08f1945670ba (patch) | |
| tree | e6e9c1269c9ed949fb89bf7d31e116ace255d2ff | |
| parent | 594592dc6f68356a3b7278eb4d260a50a66f0a06 (diff) | |
| download | linux-e4879e28abd67b894fb9d2db0afd08f1945670ba.tar.gz linux-e4879e28abd67b894fb9d2db0afd08f1945670ba.tar.bz2 linux-e4879e28abd67b894fb9d2db0afd08f1945670ba.zip | |
hwmon: (ds1621) Avoid unneeded register access
Register access over SMBus isn't cheap, so avoid register access where
possible:
* Only write back the configuration register if it changed.
* Don't refresh the register cache when we don't have to.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Aurelien Jarno <aurelien@aurel32.net>
| -rw-r--r-- | drivers/hwmon/ds1621.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/hwmon/ds1621.c b/drivers/hwmon/ds1621.c index fe160c54b959..53f88f511816 100644 --- a/drivers/hwmon/ds1621.c +++ b/drivers/hwmon/ds1621.c @@ -101,17 +101,20 @@ static int ds1621_write_temp(struct i2c_client *client, u8 reg, u16 value) static void ds1621_init_client(struct i2c_client *client) { - int reg = i2c_smbus_read_byte_data(client, DS1621_REG_CONF); + u8 conf, new_conf; + + new_conf = conf = i2c_smbus_read_byte_data(client, DS1621_REG_CONF); /* switch to continuous conversion mode */ - reg &= ~ DS1621_REG_CONFIG_1SHOT; + new_conf &= ~DS1621_REG_CONFIG_1SHOT; /* setup output polarity */ if (polarity == 0) - reg &= ~DS1621_REG_CONFIG_POLARITY; + new_conf &= ~DS1621_REG_CONFIG_POLARITY; else if (polarity == 1) - reg |= DS1621_REG_CONFIG_POLARITY; + new_conf |= DS1621_REG_CONFIG_POLARITY; - i2c_smbus_write_byte_data(client, DS1621_REG_CONF, reg); + if (conf != new_conf) + i2c_smbus_write_byte_data(client, DS1621_REG_CONF, new_conf); /* start conversion */ i2c_smbus_write_byte(client, DS1621_COM_START); @@ -170,7 +173,7 @@ static ssize_t set_temp(struct device *dev, struct device_attribute *da, { struct sensor_device_attribute *attr = to_sensor_dev_attr(da); struct i2c_client *client = to_i2c_client(dev); - struct ds1621_data *data = ds1621_update_client(dev); + struct ds1621_data *data = i2c_get_clientdata(client); u16 val = LM75_TEMP_TO_REG(simple_strtol(buf, NULL, 10)); mutex_lock(&data->update_lock); |