Make the LM75/LM75A device detection faster:
* Don't read the current temperature value when we don't use it.
* Check for unused bits in the configuration register as soon as we
have read its value.
* Don't use word reads, not all devices support this, and some which
don't misbehave when you try.
* Check for cycling register values every 40 register addresses
instead of every 8, it's 5 times faster and just as efficient.
Some of these improvements come straight from the user-space
sensors-detect script, so both detection routines are in line now.
Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
Cc: Lennart Sorensen <lsorense@xxxxxxxxxxxxxxxxxxx>
---
drivers/hwmon/lm75.c | 40 +++++++++++++++++++---------------------
1 file changed, 19 insertions(+), 21 deletions(-)
--- linux-2.6.38-rc5.orig/drivers/hwmon/lm75.c 2011-02-24 08:47:12.000000000 +0100
+++ linux-2.6.38-rc5/drivers/hwmon/lm75.c 2011-02-24 10:57:46.000000000 +0100
@@ -240,7 +240,7 @@ static int lm75_detect(struct i2c_client
{
struct i2c_adapter *adapter = new_client->adapter;
int i;
- int cur, conf, hyst, os;
+ int conf, hyst, os;
bool is_lm75a = 0;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
@@ -261,8 +261,10 @@ static int lm75_detect(struct i2c_client
register 7, and unused registers return 0xff rather than the
last read value. */
- cur = i2c_smbus_read_word_data(new_client, 0);
+ /* Unused bits */
conf = i2c_smbus_read_byte_data(new_client, 1);
+ if (conf & 0xe0)
+ return -ENODEV;
/* First check for LM75A */
if (i2c_smbus_read_byte_data(new_client, 7) == LM75A_ID) {
@@ -273,33 +275,29 @@ static int lm75_detect(struct i2c_client
|| i2c_smbus_read_byte_data(new_client, 6) != 0xff)
return -ENODEV;
is_lm75a = 1;
- hyst = i2c_smbus_read_word_data(new_client, 2);
- os = i2c_smbus_read_word_data(new_client, 3);
+ hyst = i2c_smbus_read_byte_data(new_client, 2);
+ os = i2c_smbus_read_byte_data(new_client, 3);
} else { /* Traditional style LM75 detection */
/* Unused addresses */
- hyst = i2c_smbus_read_word_data(new_client, 2);
- if (i2c_smbus_read_word_data(new_client, 4) != hyst
- || i2c_smbus_read_word_data(new_client, 5) != hyst
- || i2c_smbus_read_word_data(new_client, 6) != hyst
- || i2c_smbus_read_word_data(new_client, 7) != hyst)
+ hyst = i2c_smbus_read_byte_data(new_client, 2);
+ if (i2c_smbus_read_byte_data(new_client, 4) != hyst
+ || i2c_smbus_read_byte_data(new_client, 5) != hyst
+ || i2c_smbus_read_byte_data(new_client, 6) != hyst
+ || i2c_smbus_read_byte_data(new_client, 7) != hyst)
return -ENODEV;
- os = i2c_smbus_read_word_data(new_client, 3);
- if (i2c_smbus_read_word_data(new_client, 4) != os
- || i2c_smbus_read_word_data(new_client, 5) != os
- || i2c_smbus_read_word_data(new_client, 6) != os
- || i2c_smbus_read_word_data(new_client, 7) != os)
+ os = i2c_smbus_read_byte_data(new_client, 3);
+ if (i2c_smbus_read_byte_data(new_client, 4) != os
+ || i2c_smbus_read_byte_data(new_client, 5) != os
+ || i2c_smbus_read_byte_data(new_client, 6) != os
+ || i2c_smbus_read_byte_data(new_client, 7) != os)
return -ENODEV;
}
- /* Unused bits */
- if (conf & 0xe0)
- return -ENODEV;
-
/* Addresses cycling */
- for (i = 8; i < 0xff; i += 8) {
+ for (i = 8; i <= 248; i += 40) {
if (i2c_smbus_read_byte_data(new_client, i + 1) != conf
- || i2c_smbus_read_word_data(new_client, i + 2) != hyst
- || i2c_smbus_read_word_data(new_client, i + 3) != os)
+ || i2c_smbus_read_byte_data(new_client, i + 2) != hyst
+ || i2c_smbus_read_byte_data(new_client, i + 3) != os)
return -ENODEV;
if (is_lm75a && i2c_smbus_read_byte_data(new_client, i + 7)
!= LM75A_ID)
--
Jean Delvare
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