diff options
Diffstat (limited to 'drivers/hwmon/lm75.c')
| -rw-r--r-- | drivers/hwmon/lm75.c | 37 |
1 files changed, 24 insertions, 13 deletions
diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c index 669481baac0..90126a2a1e4 100644 --- a/drivers/hwmon/lm75.c +++ b/drivers/hwmon/lm75.c @@ -249,19 +249,30 @@ static int lm75_detect(struct i2c_client *new_client, I2C_FUNC_SMBUS_WORD_DATA)) return -ENODEV; - /* Now, we do the remaining detection. There is no identification- - dedicated register so we have to rely on several tricks: - unused bits, registers cycling over 8-address boundaries, - addresses 0x04-0x07 returning the last read value. - The cycling+unused addresses combination is not tested, - since it would significantly slow the detection down and would - hardly add any value. - - The National Semiconductor LM75A is different than earlier - LM75s. It has an ID byte of 0xaX (where X is the chip - revision, with 1 being the only revision in existence) in - register 7, and unused registers return 0xff rather than the - last read value. */ + /* + * Now, we do the remaining detection. There is no identification- + * dedicated register so we have to rely on several tricks: + * unused bits, registers cycling over 8-address boundaries, + * addresses 0x04-0x07 returning the last read value. + * The cycling+unused addresses combination is not tested, + * since it would significantly slow the detection down and would + * hardly add any value. + * + * The National Semiconductor LM75A is different than earlier + * LM75s. It has an ID byte of 0xaX (where X is the chip + * revision, with 1 being the only revision in existence) in + * register 7, and unused registers return 0xff rather than the + * last read value. + * + * Note that this function only detects the original National + * Semiconductor LM75 and the LM75A. Clones from other vendors + * aren't detected, on purpose, because they are typically never + * found on PC hardware. They are found on embedded designs where + * they can be instantiated explicitly so detection is not needed. + * The absence of identification registers on all these clones + * would make their exhaustive detection very difficult and weak, + * and odds are that the driver would bind to unsupported devices. + */ /* Unused bits */ conf = i2c_smbus_read_byte_data(new_client, 1); |