1.\" $NetBSD: powerhook_establish.9,v 1.9 2008/04/30 13:10:58 martin 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.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd September 24, 2006 31.Dt POWERHOOK_ESTABLISH 9 32.Os 33.Sh NAME 34.Nm powerhook_establish , 35.Nm powerhook_disestablish 36.Nd add or remove a power change hook 37.Sh SYNOPSIS 38.Ft void * 39.Fn powerhook_establish "const char *name" "void (*fn)(int why, void *a)" \ 40"void *arg" 41.Ft void 42.Fn powerhook_disestablish "void *cookie" 43.Sh DESCRIPTION 44The 45.Fn powerhook_establish 46function adds 47.Fa fn 48of the list of hooks invoked by 49.Xr dopowerhooks 9 50at power change. 51When invoked, the hook function 52.Fa fn 53will be passed the new power state as the first argument and 54.Fa arg 55as its second argument. 56.Pp 57The 58.Fn powerhook_disestablish 59function removes the hook described by the opaque pointer 60.Fa cookie 61from the list of hooks to be invoked at power change. 62If 63.Fa cookie 64is invalid, the result of 65.Fn powerhook_disestablish 66is undefined. 67.Pp 68Power hooks should be used to perform activities 69that must happen when the power situation to the computer changes. 70Because of the environment in which they are run, power hooks cannot 71rely on many system services (including file systems, and timeouts 72and other interrupt-driven services). 73The power hooks are typically executed from an interrupt context. 74.Pp 75The different reasons for calling the power hooks are: suspend, standby, and 76resume. 77The reason is reflected in the 78.Fa why 79argument and the values 80.Dv PWR_SOFTSUSPEND , 81.Dv PWR_SUSPEND , 82.Dv PWR_SOFTSTANDBY , 83.Dv PWR_STANDBY , 84.Dv PWR_SOFTRESUME , 85and 86.Dv PWR_RESUME . 87It calls with PWR_SOFTxxx in the normal priority level while the other 88callings are protected with 89.Xr splhigh 9 . 90At suspend the system is going to lose (almost) all power, standby retains 91some power (e.g., minimal power to USB devices), and at resume power is 92back to normal. 93.Sh RETURN VALUES 94If successful, 95.Fn powerhook_establish 96returns an opaque pointer describing the newly-established 97power hook. 98Otherwise, it returns NULL. 99.Sh SEE ALSO 100.Xr dopowerhooks 9 101