adt7462: new hwmon driver

New driver to play with.  As Jean mentioned a couple of years ago, this
chip is a beast with odd combinations of 8 fans, 4 temperatures, and 13
voltage sensors.  This driver has been tested on an IntelliStation Z30.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/Documentation/hwmon/adt7462 b/Documentation/hwmon/adt7462
new file mode 100644
index 00000000000..ec660b32827
--- /dev/null
+++ b/Documentation/hwmon/adt7462
@@ -0,0 +1,67 @@
+Kernel driver adt7462
+======================
+
+Supported chips:
+  * Analog Devices ADT7462
+    Prefix: 'adt7462'
+    Addresses scanned: I2C 0x58, 0x5C
+    Datasheet: Publicly available at the Analog Devices website
+
+Author: Darrick J. Wong
+
+Description
+-----------
+
+This driver implements support for the Analog Devices ADT7462 chip family.
+
+This chip is a bit of a beast.  It has 8 counters for measuring fan speed.  It
+can also measure 13 voltages or 4 temperatures, or various combinations of the
+two.  See the chip documentation for more details about the exact set of
+configurations.  This driver does not allow one to configure the chip; that is
+left to the system designer.
+
+A sophisticated control system for the PWM outputs is designed into the ADT7462
+that allows fan speed to be adjusted automatically based on any of the three
+temperature sensors. Each PWM output is individually adjustable and
+programmable. Once configured, the ADT7462 will adjust the PWM outputs in
+response to the measured temperatures without further host intervention.  This
+feature can also be disabled for manual control of the PWM's.
+
+Each of the measured inputs (voltage, temperature, fan speed) has
+corresponding high/low limit values. The ADT7462 will signal an ALARM if
+any measured value exceeds either limit.
+
+The ADT7462 samples all inputs continuously. The driver will not read
+the registers more often than once every other second. Further,
+configuration data is only read once per minute.
+
+Special Features
+----------------
+
+The ADT7462 have a 10-bit ADC and can therefore measure temperatures
+with 0.25 degC resolution.
+
+The Analog Devices datasheet is very detailed and describes a procedure for
+determining an optimal configuration for the automatic PWM control.
+
+The driver will report sensor labels when it is able to determine that
+information from the configuration registers.
+
+Configuration Notes
+-------------------
+
+Besides standard interfaces driver adds the following:
+
+* PWM Control
+
+* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
+* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
+
+point1: Set the pwm speed at a lower temperature bound.
+point2: Set the pwm speed at a higher temperature bound.
+
+The ADT7462 will scale the pwm between the lower and higher pwm speed when
+the temperature is between the two temperature boundaries.  PWM values range
+from 0 (off) to 255 (full speed).  Fan speed will be set to maximum when the
+temperature sensor associated with the PWM control exceeds temp#_max.
+