hwmon: (pc87427) Add temperature monitoring support

Add support for the 6 temperature monitoring channels of the PC87427.
Note that the sensors resolution can vary, and I couldn't find a way
to figure it out, so we might have to compensate in user-space.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>

Documentation/hwmon/pc87427

@@ -18,7 +18,8 @@ Description
 
 The National Semiconductor Super I/O chip includes complete hardware
 monitoring capabilities. It can monitor up to 18 voltages, 8 fans and
-6 temperature sensors. Only the fans are supported at the moment.
+6 temperature sensors. Only the fans and temperatures are supported at
+the moment, voltages aren't.
 
 This chip also has fan controlling features (up to 4 PWM outputs),
 which are partly supported by this driver.
@@ -45,3 +46,14 @@ Fan speed can be controlled by PWM outputs. There are 4 possible modes:
 always off, always on, manual and automatic. The latter isn't supported
 by the driver: you can only return to that mode if it was the original
 setting, and the configuration interface is missing.
+
+
+Temperature Monitoring
+----------------------
+
+The PC87427 relies on external sensors (following the SensorPath
+standard), so the resolution and range depend on the type of sensor
+connected. The integer part can be 8-bit or 9-bit, and can be signed or
+not. I couldn't find a way to figure out the external sensor data
+temperature format, so user-space adjustment (typically by a factor 2)
+may be required.

drivers/hwmon/Kconfig

@@ -711,8 +711,8 @@ config SENSORS_PC87427
 	  functions of the National Semiconductor PC87427 Super-I/O chip.
 	  The chip has two distinct logical devices, one for fan speed
 	  monitoring and control, and one for voltage and temperature
-	  monitoring. Only fan speed monitoring and control is supported
-	  right now.
+	  monitoring. Fan speed monitoring and control are supported, as
+	  well as temperature monitoring. Voltages aren't supported yet.
 
 	  This driver can also be built as a module.  If so, the module
 	  will be called pc87427.