>The register is a word on both chips, but >whereas lm75 stores the temperature from d14 to d8, lm77 does this from >d10 to d3: > > d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 >lm75 msb b7 b6 b5 b4 b3 b2 b1 lsb x x x x x x x >lm77 sgn sgn sgn sgn msb b7 b6 b5 b4 b3 b2 b1 b0 x x x > >where b1 is bit1, x is unused/used for other purposes. OK, that explains your strange values. BTW, d15 on lm75 is sign as well. And what's the point in lm77's having 4 bit for sign? If that means that all 4 bits will always be the same, that's something we can use for identification. >The LM77 >has support for a T_high and T_low, but I'm not sure if anyone would >need that. Well, why not. We have other chips doing this, it perfectly fits in our interface. >Maybe we could check for the existence T_high and T_low registers? We cannot. LM75 chips will not answer with an error if you try to read these registers. It will return a value, just that this value isn't relevant. I cannot remember exactly what it returns... Possible the value of register 0x03. What we may use OTOH are: * unused bits in config register if they differ; * unused bits in temperature registers; they differ, and it should be sufficent since it's VERY unlikely that ALL 4 low bits of all temperature values are 0 on a LM77 (while the same bits will read 0 on a LM75). That should be a good thing to start with; * try to learn what the LM75 would return for T_high and T_low; Do we have a dump of a LM75 chip? I think I remember Mark Hoffman has access to such a chip. Hopefully, LM75 compatible chips such as the DS75 and DS1775 will behave likewise. >That's right, I'm not interested in user-space tools and can live >without having it in the stock kernel if it turns out that noone needs >it. However these embedded boards seem to be pretty popular nowadays >(see eg. http://www.pcengines.ch for a vendor) and they have quite >complete support in the kernel apart from this one little thing... Apart from the fact that you are not interested, will you have the possibility to test things like sensors-detect (perl script) or i2cdump on the box? Thanks, Jean Delvare
