hwmon: Driver for Linear Technologies LTC2945

LTC2945 is a system monitor that measures current, voltage, and power.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

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+Kernel driver ltc2945
+=====================
+
+Supported chips:
+  * Linear Technology LTC2945
+    Prefix: 'ltc2945'
+    Addresses scanned: -
+    Datasheet:
+        http://cds.linear.com/docs/en/datasheet/2945fa.pdf
+
+Author: Guenter Roeck <linux@roeck-us.net>
+
+
+Description
+-----------
+
+The LTC2945  is a rail-to-rail system monitor that measures current, voltage,
+and power consumption.
+
+
+Usage Notes
+-----------
+
+This driver does not probe for LTC2945 devices, since there is no register
+which can be safely used to identify the chip. You will have to instantiate
+the devices explicitly.
+
+Example: the following will load the driver for an LTC2945 at address 0x10
+on I2C bus #1:
+$ modprobe ltc2945
+$ echo ltc2945 0x10 > /sys/bus/i2c/devices/i2c-1/new_device
+
+
+Sysfs entries
+-------------
+
+Voltage readings provided by this driver are reported as obtained from the ADC
+registers. If a set of voltage divider resistors is installed, calculate the
+real voltage by multiplying the reported value with (R1+R2)/R2, where R1 is the
+value of the divider resistor against the measured voltage and R2 is the value
+of the divider resistor against Ground.
+
+Current reading provided by this driver is reported as obtained from the ADC
+Current Sense register. The reported value assumes that a 1 mOhm sense resistor
+is installed. If a different sense resistor is installed, calculate the real
+current by dividing the reported value by the sense resistor value in mOhm.
+
+in1_input               VIN voltage (mV). Voltage is measured either at
+                        SENSE+ or VDD pin depending on chip configuration.
+in1_min                 Undervoltage threshold
+in1_max                 Overvoltage threshold
+in1_lowest              Lowest measured voltage
+in1_highest             Highest measured voltage
+in1_reset_history       Write 1 to reset in1 history
+in1_min_alarm           Undervoltage alarm
+in1_max_alarm           Overvoltage alarm
+
+in2_input               ADIN voltage (mV)
+in2_min                 Undervoltage threshold
+in2_max                 Overvoltage threshold
+in2_lowest              Lowest measured voltage
+in2_highest             Highest measured voltage
+in2_reset_history       Write 1 to reset in2 history
+in2_min_alarm           Undervoltage alarm
+in2_max_alarm           Overvoltage alarm
+
+curr1_input             SENSE current (mA)
+curr1_min               Undercurrent threshold
+curr1_max               Overcurrent threshold
+curr1_lowest            Lowest measured current
+curr1_highest           Highest measured current
+curr1_reset_history     Write 1 to reset curr1 history
+curr1_min_alarm         Undercurrent alarm
+curr1_max_alarm         Overcurrent alarm
+
+power1_input            Power (in uW). Power is calculated based on SENSE+/VDD
+                        voltage or ADIN voltage depending on chip configuration.
+power1_min              Low lower threshold
+power1_max              High power threshold
+power1_input_lowest     Historical minimum power use
+power1_input_highest    Historical maximum power use
+power1_reset_history    Write 1 to reset power1 history
+power1_min_alarm        Low power alarm
+power1_max_alarm        High power alarm