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 June 15, 1996 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 . 63.Pp 64Since 65.Fa uio 66normally describes user space addresses, 67.Fn physio 68needs to lock the process into memory. 69This is done by setting the 70.Dv P_PHYSIO 71flag on the process. 72.Fn physio 73always awaits the completion of the entire requested transfer before 74returning, unless an error condition is detected earlier. 75.Pp 76A break-down of the arguments follows: 77.Bl -tag -width indent 78.It Fa dev 79The device number identifying the device to interact with. 80.It Fa uio 81The description of the entire transfer as requested by the user process. 82Currently, the results of passing a 83.Fa uio 84structure with the 85.Va uio_segflg 86set to anything other than 87.Dv UIO_USERSPACE 88are undefined. 89.El 90.Sh RETURN VALUES 91If successful 92.Fn physio 93returns 0. 94.Er EFAULT 95is returned if the address range described by 96.Fa uio 97is not accessible by the requesting process. 98.Fn physio 99will return any error resulting from calls to the device strategy routine, 100by examining the 101.Dv B_ERROR 102buffer flag and the 103.Va b_error 104field. 105Note that the actual transfer size may be less than requested by 106.Fa uio 107if the device signals an 108.Dq "end of file" 109condition. 110.Sh SEE ALSO 111.Xr read 2 , 112.Xr write 2 113.Sh HISTORY 114The 115.Nm 116manual page is originally from 117.Nx 118with minor changes for applicability with 119.Fx . 120.Pp 121The 122.Nm 123call has been completely re-written for providing higher 124I/O and paging performance. 125