POWERHOOK_ESTABLISH(9) | Kernel Developer's Manual | POWERHOOK_ESTABLISH(9) |
powerhook_establish
,
powerhook_disestablish
—
powerhook_establish
(const
char *name, void (*fn)(int
why, void *a), void
*arg);
void
powerhook_disestablish
(void
*cookie);
powerhook_establish
API is deprecated.
The powerhook_establish
() function adds
fn of the list of hooks invoked by
dopowerhooks(9) at power
change. When invoked, the hook function fn will be
passed the new power state as the first argument and
arg as its second argument.
The powerhook_disestablish
() function
removes the hook described by the opaque pointer
cookie from the list of hooks to be invoked at power
change. If cookie is invalid, the result of
powerhook_disestablish
() is undefined.
Power hooks should be used to perform activities that must happen when the power situation to the computer changes. Because of the environment in which they are run, power hooks cannot rely on many system services (including file systems, and timeouts and other interrupt-driven services). The power hooks are typically executed from an interrupt context.
The different reasons for calling the power hooks are: suspend,
standby, and resume. The reason is reflected in the
why argument and the values
PWR_SOFTSUSPEND
,
PWR_SUSPEND
,
PWR_SOFTSTANDBY
,
PWR_STANDBY
, PWR_SOFTRESUME
,
and PWR_RESUME
. It calls with PWR_SOFTxxx in the
normal priority level while the other callings are protected with
splhigh(9). At suspend the
system is going to lose (almost) all power, standby retains some power
(e.g., minimal power to USB devices), and at resume power is back to
normal.
powerhook_establish
() returns an opaque
pointer describing the newly-established power hook. Otherwise, it returns
NULL.
May 14, 2009 | NetBSD 9.2 |