path: root/Documentation/hwmon
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authorGuenter Roeck <>2014-05-12 10:11:32 -0700
committerGuenter Roeck <>2014-05-21 16:02:23 -0700
commit57d60b1b7e0d0d32602587fd032d56d7ed9e1556 (patch)
tree832658f96f4dfbfadfe0aeefeacce67132f567b4 /Documentation/hwmon
parenta9622663e0406932612ffd44fde586e59df9de43 (diff)
hwmon: (emc1403) Add driver documentation
With the driver now supporting several chip variants, it is about time to document what is supported. Signed-off-by: Guenter Roeck <>
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+Kernel driver emc1403
+Supported chips:
+ * SMSC / Microchip EMC1402, EMC1412
+ Addresses scanned: I2C 0x18, 0x1c, 0x29, 0x4c, 0x4d, 0x5c
+ Prefix: 'emc1402'
+ Datasheets:
+ * SMSC / Microchip EMC1403, EMC1404, EMC1413, EMC1414
+ Addresses scanned: I2C 0x18, 0x29, 0x4c, 0x4d
+ Prefix: 'emc1403', 'emc1404'
+ Datasheets:
+ * SMSC / Microchip EMC1422
+ Addresses scanned: I2C 0x4c
+ Prefix: 'emc1422'
+ Datasheet:
+ * SMSC / Microchip EMC1423, EMC1424
+ Addresses scanned: I2C 0x4c
+ Prefix: 'emc1423', 'emc1424'
+ Datasheet:
+ Kalhan Trisal <
+The Standard Microsystems Corporation (SMSC) / Microchip EMC14xx chips
+contain up to four temperature sensors. EMC14x2 support two sensors
+(one internal, one external). EMC14x3 support three sensors (one internal,
+two external), and EMC14x4 support four sensors (one internal, three
+The chips implement three limits for each sensor: low (tempX_min), high
+(tempX_max) and critical (tempX_crit.) The chips also implement an
+hysteresis mechanism which applies to all limits. The relative difference
+is stored in a single register on the chip, which means that the relative
+difference between the limit and its hysteresis is always the same for
+all three limits.
+This implementation detail implies the following:
+* When setting a limit, its hysteresis will automatically follow, the
+ difference staying unchanged. For example, if the old critical limit
+ was 80 degrees C, and the hysteresis was 75 degrees C, and you change
+ the critical limit to 90 degrees C, then the hysteresis will
+ automatically change to 85 degrees C.
+* While hysteresis limits can be set for all critical limits, setting a single
+ hysteresis value affects the hysteresis values for all limits on all sensors.
+* The limits should be set before the hysteresis.