On Thu, Oct 13, 2011 at 05:15:11PM -0400, Jean Delvare wrote: > Explain why clones of the LM75 are generally not detected by the > driver, and why this isn't going to change. Also update the > documentation to reflect the list of chip names currently supported by > the driver. > > Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx> Applied to -next. Thanks, Guenter > --- > Documentation/hwmon/lm75 | 58 ++++++++++++++++++++++++++-------------------- > drivers/hwmon/lm75.c | 37 +++++++++++++++++++---------- > 2 files changed, 58 insertions(+), 37 deletions(-) > > --- linux-3.1-rc9.orig/drivers/hwmon/lm75.c 2011-10-13 22:52:01.000000000 +0200 > +++ linux-3.1-rc9/drivers/hwmon/lm75.c 2011-10-13 22:52:10.000000000 +0200 > @@ -249,19 +249,30 @@ static int lm75_detect(struct i2c_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); > --- linux-3.1-rc9.orig/Documentation/hwmon/lm75 2011-10-13 22:52:01.000000000 +0200 > +++ linux-3.1-rc9/Documentation/hwmon/lm75 2011-10-13 23:07:02.000000000 +0200 > @@ -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@xxxxxx> > > @@ -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. > > > -- > Jean Delvare _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
