1.\" $NetBSD: powerhook_establish.9,v 1.3 2001/06/21 11:59:01 wiz Exp $ 2.\" 3.\" Copyright (c) 1999 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Lennart Augustsson. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd December 3, 1999 38.Dt POWERHOOK_ESTABLISH 9 39.Os 40.Sh NAME 41.Nm powerhook_establish , 42.Nm powerhook_disestablish 43.Nd add or remove a power change hook 44.Sh SYNOPSIS 45.Ft void * 46.Fn powerhook_establish "void (*fn)(int why, void *a)" "void *arg" 47.Ft void 48.Fn powerhook_disestablish "void *cookie" 49.Sh DESCRIPTION 50The 51.Fn powerhook_establish 52function adds 53.Fa fn 54of the list of hooks invoked by 55.Xr dopowerhooks 9 56at power change. When invoked, the hook function 57.Fa fn 58will be passed the new power state as the first argument and 59.Fa arg 60as its second argument. 61.Pp 62The 63.Fn powerhook_disestablish 64function removes the hook described by the opaque pointer 65.Fa cookie 66from the list of hooks to be invoked at power change. If 67.Fa cookie 68is invalid, the result of 69.Fn powerhook_disestablish 70is undefined. 71.Pp 72Power hooks should be used to perform activities 73that must happen when the power situation to the computer changes. Because 74of the environment in which they are run, shutdown hooks cannot 75rely on many system services (including file systems, and timeouts 76and other interrupt-driven services). 77The power hooks are typically executed from an interrupt context. 78.Pp 79The different reasons for calling the power hooks are: suspend, standby, and 80resume. The reason is reflected in the 81.Fa why 82argument and the values 83.Dv PWR_SOFTSUSPEND , 84.Dv PWR_SUSPEND , 85.Dv PWR_SOFTSTANDBY , 86.Dv PWR_STANDBY , 87.Dv PWR_SOFTRESUME , 88and 89.Dv PWR_RESUME . 90It calls with PWR_SOFTxxx in the normal priority level while the other 91callings are protected with 92.Xr splhigh 9 . 93At suspend the system is going to lose (almost) all power, standby retains 94some power (e.g., minimal power to USB devices), and at resume power is 95back to normal. 96.Sh RETURN VALUES 97If successful, 98.Fn powerhook_establish 99returns an opaque pointer describing the newly-established 100shutdown hook. Otherwise, it returns NULL. 101.Sh SEE ALSO 102.Xr dopowerhooks 9 103