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.\" 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 REGENTS OR CONTRIBUTORS BE 22.\" 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 January 19, 2012 31.Dt PHYSIO 9 32.Os 33.Sh NAME 34.Nm physio 35.Nd initiate I/O on raw devices 36.Sh SYNOPSIS 37.In sys/param.h 38.In sys/systm.h 39.In sys/bio.h 40.In sys/buf.h 41.Ft int 42.Fn physio "struct cdev *dev" "struct uio *uio" "int ioflag" 43.Sh DESCRIPTION 44The 45.Fn physio 46is a helper function typically called from character device 47.Fn read 48and 49.Fn write 50routines to start I/O on a user process buffer. 51The maximum amount of data to transfer with each call 52is determined by 53.Fa dev->si_iosize_max . 54The 55.Fn physio 56call converts the I/O request into a 57.Fn strategy 58request and passes the new request to the driver's 59.Fn strategy 60routine for processing. 61.Pp 62Since 63.Fa uio 64normally describes user space addresses, 65.Fn physio 66needs to lock those pages into memory. 67This is done by calling 68.Fn vmapbuf 69for the appropriate pages. 70.Fn physio 71always awaits the completion of the entire requested transfer before 72returning, unless an error condition is detected earlier. 73.Pp 74A break-down of the arguments follows: 75.Bl -tag -width indent 76.It Fa dev 77The device number identifying the device to interact with. 78.It Fa uio 79The description of the entire transfer as requested by the user process. 80Currently, the results of passing a 81.Fa uio 82structure with the 83.Va uio_segflg 84set to anything other than 85.Dv UIO_USERSPACE 86are undefined. 87.It Fa ioflag 88The ioflag argument from the 89.Fn read 90or 91.Fn write 92function calling 93.Fn physio . 94.El 95.Sh RETURN VALUES 96If successful 97.Fn physio 98returns 0. 99.Er EFAULT 100is returned if the address range described by 101.Fa uio 102is not accessible by the requesting process. 103.Fn physio 104will return any error resulting from calls to the device strategy routine, 105by examining the 106.Dv B_ERROR 107buffer flag and the 108.Va b_error 109field. 110Note that the actual transfer size may be less than requested by 111.Fa uio 112if the device signals an 113.Dq "end of file" 114condition. 115.Sh SEE ALSO 116.Xr read 2 , 117.Xr write 2 118.Sh HISTORY 119The 120.Nm 121manual page is originally from 122.Nx 123with minor changes for applicability with 124.Fx . 125.Pp 126The 127.Nm 128call has been completely re-written for providing higher 129I/O and paging performance. 130