tree 7c3619d61d1f662bd29389fe34d3e3ba984af0e6
parent 86e58fffbb3a889beb2e306464929819dbf97986
author Patrick Venture <venture@google.com> 1536945554 -0700
committer Patrick Venture <venture@google.com> 1537550774 -0700

Use gpioplus for specifying gpio gating

A GPIO can control whether a hwmon sensor is readable.  This module
allows one to specify whether a sensor is gated and by what GPIO.  This
is often the case for battery voltages, such that the battery isn't
drained constantly by being left open.

For each sensor where you need GPIO locking:
GPIOCHIP_in1=0
GPIO_in1=53

such that GPIOCHIP is the gpiochip: /sys/bus/gpio/devices/gpiochip{id}
such that GPIO is the line offset.
the value used to unlock the sensor via gpio is 1
after 1 is written to the gpio, it pauses for 500ms

Tested: Verified the failure case for invalid gpio fields.  Verified
correct behavior on two platforms.
Change-Id: I2fa12848972075cad0e0f69c0bfa6382e15d4f50
Signed-off-by: Patrick Venture <venture@google.com>