fan2: /* Name of the sensor. */
  type: fan /* Type of sensor, fan, temp, margin */
  /* How the sensor can be read[1] */
  readPath: /xyz/openbmc_project/sensors/fan_tach/fan2
  /* How the sensor can be set[2] */
  writePath: /sys/class/hwmon/hwmon0/pwm1
  /* The minimum value used for scaling writes (int64) */
  min: 0
  /* The maximum value used for scaling writes (int64) */
  max: 255
  /* The timeout value for the sensor, used for failsafe, 0 means no timeout
   * (int64)
   */
  timeout: 0

[1] readPath has multiple options:
* If it has "/xyz/openbmc_project/extsensors/" in it, it's an EXTERNAL or
  host-provided sensor.
* If it has "/xyz/openbmc_project/" in it, it's a sensor whose value is
  received passively over dbus.
* If it has "/sys/" in it, it's a sensor read directly from sysfs.

[2]
* This can be left blank if the sensor is read-only.
* If it has "/sys/" in it, it's a sensor written to sysfs.
  * If min and max are non-zero, it'll convert the value to within the range.
    and output that modified value.  So, if it receives a value of .90 and min
    is 0, and max is 255, it'll convert that to a value of 229.5 that is then
    cast to int64_t.