1.\" $NetBSD: powerhook_establish.9,v 1.8 2006/09/24 07:27:57 dogcow 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 September 24, 2006 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 "const char *name" "void (*fn)(int why, void *a)" \ 47"void *arg" 48.Ft void 49.Fn powerhook_disestablish "void *cookie" 50.Sh DESCRIPTION 51The 52.Fn powerhook_establish 53function adds 54.Fa fn 55of the list of hooks invoked by 56.Xr dopowerhooks 9 57at power change. 58When invoked, the hook function 59.Fa fn 60will be passed the new power state as the first argument and 61.Fa arg 62as its second argument. 63.Pp 64The 65.Fn powerhook_disestablish 66function removes the hook described by the opaque pointer 67.Fa cookie 68from the list of hooks to be invoked at power change. 69If 70.Fa cookie 71is invalid, the result of 72.Fn powerhook_disestablish 73is undefined. 74.Pp 75Power hooks should be used to perform activities 76that must happen when the power situation to the computer changes. 77Because of the environment in which they are run, power hooks cannot 78rely on many system services (including file systems, and timeouts 79and other interrupt-driven services). 80The power hooks are typically executed from an interrupt context. 81.Pp 82The different reasons for calling the power hooks are: suspend, standby, and 83resume. 84The reason is reflected in the 85.Fa why 86argument and the values 87.Dv PWR_SOFTSUSPEND , 88.Dv PWR_SUSPEND , 89.Dv PWR_SOFTSTANDBY , 90.Dv PWR_STANDBY , 91.Dv PWR_SOFTRESUME , 92and 93.Dv PWR_RESUME . 94It calls with PWR_SOFTxxx in the normal priority level while the other 95callings are protected with 96.Xr splhigh 9 . 97At suspend the system is going to lose (almost) all power, standby retains 98some power (e.g., minimal power to USB devices), and at resume power is 99back to normal. 100.Sh RETURN VALUES 101If successful, 102.Fn powerhook_establish 103returns an opaque pointer describing the newly-established 104power hook. 105Otherwise, it returns NULL. 106.Sh SEE ALSO 107.Xr dopowerhooks 9 108