On Mon, 29 Oct 2012 08:37:31 -0700, Guenter Roeck wrote:
> On Mon, Oct 29, 2012 at 11:08:30AM +0100, Jean Delvare wrote:
> > On Sun, 28 Oct 2012 11:19:56 -0700, Guenter Roeck wrote:
> > > diff --git a/drivers/hwmon/it87.c b/drivers/hwmon/it87.c
> > > index 82f7924..fe2cdd4 100644
> > > --- a/drivers/hwmon/it87.c
> > > +++ b/drivers/hwmon/it87.c
> > > @@ -203,6 +203,8 @@ static const u8 IT87_REG_FAN[] = { 0x0d, 0x0e, 0x0f, 0x80, 0x82 };
> > > static const u8 IT87_REG_FAN_MIN[] = { 0x10, 0x11, 0x12, 0x84, 0x86 };
> > > static const u8 IT87_REG_FANX[] = { 0x18, 0x19, 0x1a, 0x81, 0x83 };
> > > static const u8 IT87_REG_FANX_MIN[] = { 0x1b, 0x1c, 0x1d, 0x85, 0x87 };
> > > +static const u8 IT87_REG_TEMP_OFFSET[] = { 0x56, 0x57, 0x59 };
> >
> > Not all supported chips have these registers. For example, the IT8712F
> > rev. D doesn't have registers at 0x56 and 0x57, and register 0x59
> > apparently adjusts the offset for all 3 temperature channels. Also the
> > value is expressed as a reference voltage, not an offset in degrees C:
> >
> > "Thermal Diode Zero Degree Voltage value (default: 0.664V 156h)."
> >
> > (I don't quite understand how they can make 156h fit in an 8-bit
> > register, but that a different problem.)
> >
> > So you will have to check all chips and revisions for support and only
> > create the sysfs attributes if the chip supports per-channel, degree C
> > offsets. A quick grep suggests that even the latest IT8705F and IT8712F
> > chip revisons had a voltage value in these registers, so support would
> > start with the IT8716F.
>
> Actually, I did check all chip revisions for which I have documentation.
>
> I have the following datasheets:
> IT8705F rev. 0.4 (chip revision 3)
> IT8712F rev. 0.7 (chip revision 6)
> IT8712F rev. 0.81 (chip revision 7)
>
> In all those specifications, the registers exist and are called "Thermal Diode
> Zero Degree Adjust {1|2|3} Register".
Right, but the contents are different from what later chips have. The
default value (56h) and description (Zero Degree *Voltage Value*) make
it quite clear to me.
> Kind of odd (and a bit scary) that they would remove the registers with later
> chip revisions. Anyway, I'll have to see if I can find any additional versions
> of the specifications.
No, they did not remove these in later chip revisions. They changed the
register unit/values with the IT8716F.
> Maybe I should simply drop the attributes for IT8705F and IT8712F ?
Agreed.
--
Jean Delvare
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