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+Kernel driver adt7470
+Supported chips:
+ * Analog Devices ADT7470
+ Prefix: 'adt7470'
+ Addresses scanned: I2C 0x2C, 0x2E, 0x2F
+ Datasheet: Publicly available at the Analog Devices website
+Author: Darrick J. Wong
+This driver implements support for the Analog Devices ADT7470 chip. There may
+be other chips that implement this interface.
+The ADT7470 uses the 2-wire interface compatible with the SMBus 2.0
+specification. Using an analog to digital converter it measures up to ten (10)
+external temperatures. It has four (4) 16-bit counters for measuring fan speed.
+There are four (4) PWM outputs that can be used to control fan speed.
+A sophisticated control system for the PWM outputs is designed into the ADT7470
+that allows fan speed to be adjusted automatically based on any of the ten
+temperature sensors. Each PWM output is individually adjustable and
+programmable. Once configured, the ADT7470 will adjust the PWM outputs in
+response to the measured temperatures with further host intervention. This
+feature can also be disabled for manual control of the PWM's.
+Each of the measured inputs (temperature, fan speed) has corresponding high/low
+limit values. The ADT7470 will signal an ALARM if any measured value exceeds
+either limit.
+The ADT7470 samples all inputs continuously. A kernel thread is started up for
+the purpose of periodically querying the temperature sensors, thus allowing the
+automatic fan pwm control to set the fan speed. The driver will not read the
+registers more often than once every 5 seconds. Further, configuration data is
+only read once per minute.
+Special Features
+The ADT7470 has a 8-bit ADC and is capable of measuring temperatures with 1
+degC resolution.
+The Analog Devices datasheet is very detailed and describes a procedure for
+determining an optimal configuration for the automatic PWM control.
+Configuration Notes
+Besides standard interfaces driver adds the following:
+* PWM Control
+* pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
+* pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
+point1: Set the pwm speed at a lower temperature bound.
+point2: Set the pwm speed at a higher temperature bound.
+The ADT7470 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
+The temperature inputs no longer need to be read periodically from userspace in
+order for the automatic pwm algorithm to run. This was the case for earlier
+versions of the driver.