diff options
| -rw-r--r-- | Documentation/hwmon/lm75 | 58 | ||||
| -rw-r--r-- | drivers/hwmon/lm75.c | 37 |
2 files changed, 58 insertions, 37 deletions
diff --git a/Documentation/hwmon/lm75 b/Documentation/hwmon/lm75 index 8d40d0fda10a..c91a1d15fa28 100644 --- a/Documentation/hwmon/lm75 +++ b/Documentation/hwmon/lm75 @@ -12,31 +12,46 @@ Supported chips: Addresses scanned: I2C 0x48 - 0x4f Datasheet: Publicly available at the National Semiconductor website http://www.national.com/ - * Dallas Semiconductor DS75 - Prefix: 'lm75' - Addresses scanned: I2C 0x48 - 0x4f - Datasheet: Publicly available at the Dallas Semiconductor website - http://www.maxim-ic.com/ - * Dallas Semiconductor DS1775 - Prefix: 'lm75' - Addresses scanned: I2C 0x48 - 0x4f + * Dallas Semiconductor DS75, DS1775 + Prefixes: 'ds75', 'ds1775' + Addresses scanned: none Datasheet: Publicly available at the Dallas Semiconductor website http://www.maxim-ic.com/ * Maxim MAX6625, MAX6626 - Prefix: 'lm75' - Addresses scanned: I2C 0x48 - 0x4b + Prefixes: 'max6625', 'max6626' + Addresses scanned: none Datasheet: Publicly available at the Maxim website http://www.maxim-ic.com/ * Microchip (TelCom) TCN75 Prefix: 'lm75' - Addresses scanned: I2C 0x48 - 0x4f + Addresses scanned: none + Datasheet: Publicly available at the Microchip website + http://www.microchip.com/ + * Microchip MCP9800, MCP9801, MCP9802, MCP9803 + Prefix: 'mcp980x' + Addresses scanned: none Datasheet: Publicly available at the Microchip website http://www.microchip.com/ * Analog Devices ADT75 Prefix: 'adt75' - Addresses scanned: I2C 0x48 - 0x4f + Addresses scanned: none Datasheet: Publicly available at the Analog Devices website http://www.analog.com/adt75 + * ST Microelectronics STDS75 + Prefix: 'stds75' + Addresses scanned: none + Datasheet: Publicly available at the ST website + http://www.st.com/internet/analog/product/121769.jsp + * Texas Instruments TMP100, TMP101, TMP105, TMP75, TMP175, TMP275 + Prefixes: 'tmp100', 'tmp101', 'tmp105', 'tmp175', 'tmp75', 'tmp275' + Addresses scanned: none + Datasheet: Publicly available at the Texas Instruments website + http://www.ti.com/product/tmp100 + http://www.ti.com/product/tmp101 + http://www.ti.com/product/tmp105 + http://www.ti.com/product/tmp75 + http://www.ti.com/product/tmp175 + http://www.ti.com/product/tmp275 Author: Frodo Looijaard <frodol@dds.nl> @@ -55,21 +70,16 @@ range of -55 to +125 degrees. The LM75 only updates its values each 1.5 seconds; reading it more often will do no harm, but will return 'old' values. -The LM75 is usually used in combination with LM78-like chips, to measure -the temperature of the processor(s). - -The DS75, DS1775, MAX6625, and MAX6626 are supported as well. -They are not distinguished from an LM75. While most of these chips -have three additional bits of accuracy (12 vs. 9 for the LM75), -the additional bits are not supported. Not only that, but these chips will -not be detected if not in 9-bit precision mode (use the force parameter if -needed). - -The TCN75 is supported as well, and is not distinguished from an LM75. +The original LM75 was typically used in combination with LM78-like chips +on PC motherboards, to measure the temperature of the processor(s). Clones +are now used in various embedded designs. The LM75 is essentially an industry standard; there may be other LM75 clones not listed here, with or without various enhancements, -that are supported. +that are supported. The clones are not detected by the driver, unless +they reproduce the exact register tricks of the original LM75, and must +therefore be instantiated explicitly. The specific enhancements (such as +higher resolution) are not currently supported by the driver. The LM77 is not supported, contrary to what we pretended for a long time. Both chips are simply not compatible, value encoding differs. diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c index 669481baac00..90126a2a1e44 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); |