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- Kernel driver lm87
- ==================
- Supported chips:
- * National Semiconductor LM87
- Prefix: 'lm87'
- Addresses scanned: I2C 0x2c - 0x2f
- Datasheet: http://www.national.com/pf/LM/LM87.html
- Authors:
- Frodo Looijaard <frodol@dds.nl>,
- Philip Edelbrock <phil@netroedge.com>,
- Mark Studebaker <mdsxyz123@yahoo.com>,
- Stephen Rousset <stephen.rousset@rocketlogix.com>,
- Dan Eaton <dan.eaton@rocketlogix.com>,
- Jean Delvare <khali@linux-fr.org>,
- Original 2.6 port Jeff Oliver
- Description
- -----------
- This driver implements support for the National Semiconductor LM87.
- The LM87 implements up to three temperature sensors, up to two fan
- rotation speed sensors, up to seven voltage sensors, alarms, and some
- miscellaneous stuff.
- Temperatures are measured in degrees Celsius. Each input has a high
- and low alarm settings. A high limit produces an alarm when the value
- goes above it, and an alarm is also produced when the value goes below
- the low limit.
- Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
- triggered if the rotation speed has dropped below a programmable limit. Fan
- readings can be divided by a programmable divider (1, 2, 4 or 8) to give
- the readings more range or accuracy. Not all RPM values can accurately be
- represented, so some rounding is done. With a divider of 2, the lowest
- representable value is around 2600 RPM.
- Voltage sensors (also known as IN sensors) report their values in
- volts. An alarm is triggered if the voltage has crossed a programmable
- minimum or maximum limit. Note that minimum in this case always means
- 'closest to zero'; this is important for negative voltage measurements.
- If an alarm triggers, it will remain triggered until the hardware register
- is read at least once. This means that the cause for the alarm may
- already have disappeared! Note that in the current implementation, all
- hardware registers are read whenever any data is read (unless it is less
- than 1.0 seconds since the last update). This means that you can easily
- miss once-only alarms.
- The lm87 driver only updates its values each 1.0 seconds; reading it more
- often will do no harm, but will return 'old' values.
- Hardware Configurations
- -----------------------
- The LM87 has four pins which can serve one of two possible functions,
- depending on the hardware configuration.
- Some functions share pins, so not all functions are available at the same
- time. Which are depends on the hardware setup. This driver assumes that
- the BIOS configured the chip correctly. In that respect, it differs from
- the original driver (from lm_sensors for Linux 2.4), which would force the
- LM87 to an arbitrary, compile-time chosen mode, regardless of the actual
- chipset wiring.
- For reference, here is the list of exclusive functions:
- - in0+in5 (default) or temp3
- - fan1 (default) or in6
- - fan2 (default) or in7
- - VID lines (default) or IRQ lines (not handled by this driver)
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