hwmon: New PC87427 hardware monitoring driver

This is a new hardware monitoring driver for the National Semiconductor
PC87427 Super-I/O chip. It only supports fan speed monitoring for now,
while the chip can do much more.

Thanks to Amir Habibi at Candelis for setting up a test system, and to
Michael Kress for testing several iterations of this driver.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/hwmon/pc87427

@@ -0,0 +1,38 @@
+Kernel driver pc87427
+=====================
+
+Supported chips:
+  * National Semiconductor PC87427
+    Prefix: 'pc87427'
+    Addresses scanned: none, address read from Super I/O config space
+    Datasheet: http://www.winbond.com.tw/E-WINBONDHTM/partner/apc_007.html
+
+Author: Jean Delvare <khali@linux-fr.org>
+
+Thanks to Amir Habibi at Candelis for setting up a test system, and to
+Michael Kress for testing several iterations of this driver.
+
+
+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.
+
+This chip also has fan controlling features, which are not yet supported
+by this driver either.
+
+The driver assumes that no more than one chip is present, which seems
+reasonable.
+
+
+Fan Monitoring
+--------------
+
+Fan rotation speeds are reported as 14-bit values from a gated clock
+signal. Speeds down to 83 RPM can be measured.
+
+An alarm is triggered if the rotation speed drops below a programmable
+limit. Another alarm is triggered if the speed is too low to to be measured
+(including stalled or missing fan).

drivers/hwmon/Kconfig

@@ -353,6 +353,19 @@ config SENSORS_PC87360
 	  This driver can also be built as a module.  If so, the module
 	  will be called pc87360.
 
+config SENSORS_PC87427
+	tristate "National Semiconductor PC87427"
+	depends on HWMON && EXPERIMENTAL
+	help
+	  If you say yes here you get access to the hardware monitoring
+	  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 is supported right now.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called pc87427.
+
 config SENSORS_SIS5595
 	tristate "Silicon Integrated Systems Corp. SiS5595"
 	depends on HWMON && I2C && PCI && EXPERIMENTAL

drivers/hwmon/Makefile

@@ -41,6 +41,7 @@ obj-$(CONFIG_SENSORS_LM90)	+= lm90.o
 obj-$(CONFIG_SENSORS_LM92)	+= lm92.o
 obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
 obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
+obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o
 obj-$(CONFIG_SENSORS_SIS5595)	+= sis5595.o
 obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
 obj-$(CONFIG_SENSORS_SMSC47M1)	+= smsc47m1.o