tree 32e9785ad3bde8f6360e22365889a6fad3f28957
parent 754d38cffae079a2efa43735c013d792e8f01500
author Chiabing Lee <chiabinglee@gmail.com> 1504684706 +0800
committer Chiabing Lee <chiabinglee@gmail.com> 1505359364 +0800

Enhancement to support GAIN and OFFSET value for sensor reading

For example, AST BMC chips ADC input voltage range is 0 to 2.5V,
good nominal input voltage is 1.8V. Other voltages are scaled into
that range using external resistors(ADC voltage divider).

Since the values of these resistors can change from their own
motherboard design, the conversions cannot be hard coded into
the Linux driver and have to be done in user space.

In the sensor configuration file, add the GAIN_in[0-*] and OFFSET_in[0-*]
value.
The sensor reading conversion can be:

    value = (raw sensor reading) * gain + offset

Resolves: openbmc/openbmc#2259

Change-Id: I2502c656e0d34dd69b9c795788505f209a77a72b
Signed-off-by: Chiabing Lee <chiabinglee@gmail.com>
Signed-off-by: Lei YU <mine260309@gmail.com>