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+This describes the interface for the ADT7475 driver:
+
+(there are 4 fans, numbered fan1 to fan4):
+
+fanX_input              Read the current speed of the fan (in RPMs)
+fanX_min                Read/write the minimum speed of the fan.  Dropping
+                        below this sets an alarm.
+
+(there are three PWMs, numbered pwm1 to pwm3):
+
+pwmX                    Read/write the current duty cycle of the PWM.  Writes
+                        only have effect when auto mode is turned off (see
+                        below).  Range is 0 - 255.
+
+pwmX_enable             Fan speed control method:
+
+                        0 - No control (fan at full speed)
+                        1 - Manual fan speed control (using pwm[1-*])
+                        2 - Automatic fan speed control
+
+pwmX_auto_channels_temp Select which channels affect this PWM
+
+                        1 - TEMP1 controls PWM
+                        2 - TEMP2 controls PWM
+                        4 - TEMP3 controls PWM
+                        6 - TEMP2 and TEMP3 control PWM
+                        7 - All three inputs control PWM
+
+pwmX_freq               Read/write the PWM frequency in Hz. The number
+                        should be one of the following:
+
+                        11 Hz
+                        14 Hz
+                        22 Hz
+                        29 Hz
+                        35 Hz
+                        44 Hz
+                        58 Hz
+                        88 Hz
+
+pwmX_auto_point1_pwm    Read/write the minimum PWM duty cycle in automatic mode
+
+pwmX_auto_point2_pwm    Read/write the maximum PWM duty cycle in automatic mode
+
+(there are three temperature settings numbered temp1 to temp3):
+
+tempX_input             Read the current temperature.  The value is in milli
+                        degrees of Celsius.
+
+tempX_max               Read/write the upper temperature limit - exceeding this
+                        will cause an alarm.
+
+tempX_min               Read/write the lower temperature limit - exceeding this
+                        will cause an alarm.
+
+tempX_offset            Read/write the temperature adjustment offset
+
+tempX_crit              Read/write the THERM limit for remote1.
+
+tempX_crit_hyst         Set the temperature value below crit where the
+                        fans will stay on - this helps drive the temperature
+                        low enough so it doesn't stay near the edge and
+                        cause THERM to keep tripping.
+
+tempX_auto_point1_temp  Read/write the minimum temperature where the fans will
+                        turn on in automatic mode.
+
+tempX_auto_point2_temp  Read/write the maximum temperature over which the fans
+                        will run in automatic mode.  tempX_auto_point1_temp
+                        and tempX_auto_point2_temp together define the
+                        range of automatic control.
+
+tempX_alarm             Read a 1 if the max/min alarm is set
+tempX_fault             Read a 1 if either temp1 or temp3 diode has a fault
+
+(There are two voltage settings, in1 and in2):
+
+inX_input               Read the current voltage on VCC.  Value is in
+                        millivolts.
+
+inX_min                 read/write the minimum voltage limit.
+                        Dropping below this causes an alarm.
+
+inX_max                 read/write the maximum voltage limit.
+                        Exceeding this causes an alarm.
+
+inX_alarm               Read a 1 if the max/min alarm is set.