1.\" $NetBSD: physio.9,v 1.2 1996/11/11 00:05:12 lukem Exp $ 2.\" 3.\" Copyright (c) 1996 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Paul Kranenburg. 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 REGENTS OR CONTRIBUTORS BE 29.\" 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.\" $FreeBSD$ 38.\" 39.Dd July 8, 2004 40.Dt PHYSIO 9 41.Os 42.Sh NAME 43.Nm physio 44.Nd initiate I/O on raw devices 45.Sh SYNOPSIS 46.In sys/param.h 47.In sys/systm.h 48.In sys/bio.h 49.In sys/buf.h 50.Ft int 51.Fn physio "dev_t dev" "struct uio *uio" "int ioflag" 52.Sh DESCRIPTION 53The 54.Fn physio 55is a helper function typically called from character device 56.Fn read 57and 58.Fn write 59routines to start I/O on a user process buffer. 60The maximum amount of data to transfer with each call 61is determined by 62.Fa dev->si_iosize_max . 63The 64.Fn physio 65call converts the I/O request into a 66.Fn strategy 67request and passes the new request to the driver's 68.Fn strategy 69routine for processing. 70.Pp 71Since 72.Fa uio 73normally describes user space addresses, 74.Fn physio 75needs to lock those pages into memory. 76This is done by calling 77.Fn vmapbuf 78for the appropriate pages. 79.Fn physio 80always awaits the completion of the entire requested transfer before 81returning, unless an error condition is detected earlier. 82.Pp 83A break-down of the arguments follows: 84.Bl -tag -width indent 85.It Fa dev 86The device number identifying the device to interact with. 87.It Fa uio 88The description of the entire transfer as requested by the user process. 89Currently, the results of passing a 90.Fa uio 91structure with the 92.Va uio_segflg 93set to anything other than 94.Dv UIO_USERSPACE 95are undefined. 96.It Fa ioflag 97The ioflag argument from the 98.Fn read 99or 100.Fn write 101function calling 102.Fn physio . 103.El 104.Sh RETURN VALUES 105If successful 106.Fn physio 107returns 0. 108.Er EFAULT 109is returned if the address range described by 110.Fa uio 111is not accessible by the requesting process. 112.Fn physio 113will return any error resulting from calls to the device strategy routine, 114by examining the 115.Dv B_ERROR 116buffer flag and the 117.Va b_error 118field. 119Note that the actual transfer size may be less than requested by 120.Fa uio 121if the device signals an 122.Dq "end of file" 123condition. 124.Sh SEE ALSO 125.Xr read 2 , 126.Xr write 2 127.Sh HISTORY 128The 129.Nm 130manual page is originally from 131.Nx 132with minor changes for applicability with 133.Fx . 134.Pp 135The 136.Nm 137call has been completely re-written for providing higher 138I/O and paging performance. 139