text: DOPOWERHOOKS(9) BSD Kernel Manual DOPOWERHOOKS(9)
  dopowerhooks - run all power hooks
  #include <sys/types.h> #include <sys/systm.h> void dopowerhooks(int why);
  The dopowerhooks() function invokes all power hooks established using the powerhook_establish(9) function. At "suspend" and "standby" time, power hooks are called in reverse order, i.e., the power hook established last will be called first. At "resume" time, power hooks are called in order, i.e., the power hook established first will be called first. This routine is called from the apm(4) driver when a power change is detected. The why argument is one of PWR_SUSPEND, PWR_STANDBY, or PWR_RESUME, describing the reason for the change in power state. Each es- tablished power hook is passed this information so the appropriate ac- tions can be taken.
  apm(4), powerhook_establish.