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authorMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-04-17 12:46:29 +0300
committerGuenter Roeck <linux@roeck-us.net>2019-04-17 20:37:23 +0300
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tree9db30159bd32bec125c7d49e80a79bb7c4da0c8e /Documentation/hwmon/pc87427.rst
parentb04f2f7d387b3160883c2a1f5e2285483a791e82 (diff)
downloadlinux-7ebd8b66dd9e5a0b65e5ee5e2b8e7ca382ec97b7.tar.xz
docs: hwmon: Add an index file and rename docs to *.rst
Now that all files were converted to ReST format, rename them and add an index. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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+Kernel driver pc87427
+=====================
+
+Supported chips:
+
+ * National Semiconductor PC87427
+
+ Prefix: 'pc87427'
+
+ Addresses scanned: none, address read from Super I/O config space
+
+ Datasheet: No longer available
+
+Author: Jean Delvare <jdelvare@suse.de>
+
+Thanks to Amir Habibi at Candelis for setting up a test system, and to
+Michael Kress for testing several iterations of this driver.
+
+
+Description
+-----------
+
+The National Semiconductor Super I/O chip includes complete hardware
+monitoring capabilities. It can monitor up to 18 voltages, 8 fans and
+6 temperature sensors. Only the fans and temperatures are supported at
+the moment, voltages aren't.
+
+This chip also has fan controlling features (up to 4 PWM outputs),
+which are partly supported by this driver.
+
+The driver assumes that no more than one chip is present, which seems
+reasonable.
+
+
+Fan Monitoring
+--------------
+
+Fan rotation speeds are reported as 14-bit values from a gated clock
+signal. Speeds down to 83 RPM can be measured.
+
+An alarm is triggered if the rotation speed drops below a programmable
+limit. Another alarm is triggered if the speed is too low to be measured
+(including stalled or missing fan).
+
+
+Fan Speed Control
+-----------------
+
+Fan speed can be controlled by PWM outputs. There are 4 possible modes:
+always off, always on, manual and automatic. The latter isn't supported
+by the driver: you can only return to that mode if it was the original
+setting, and the configuration interface is missing.
+
+
+Temperature Monitoring
+----------------------
+
+The PC87427 relies on external sensors (following the SensorPath
+standard), so the resolution and range depend on the type of sensor
+connected. The integer part can be 8-bit or 9-bit, and can be signed or
+not. I couldn't find a way to figure out the external sensor data
+temperature format, so user-space adjustment (typically by a factor 2)
+may be required.