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 read and write 56routines to start I/O on a user process buffer. 57The maximum amount of data to transfer with each call 58is determined by: 59.Bd -literal 60dev->si_iosize_max 61.Ed 62.Pp 63Since 64.Fa uio 65normally describes user space addresses, 66.Fn physio 67needs to lock the process into memory. This is done by setting the 68.Dv P_PHYSIO 69flag on the process. 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.Sq uio_segflg 84set to anything other than 85.Dv UIO_USERSPACE , 86are undefined. 87.El 88.Sh RETURN VALUES 89If successful 90.Fn physio 91returns 0. 92.Er EFAULT 93is returned if the address range described by 94.Fa uio 95is not accessible by the requesting process. 96.Fn physio 97will return any error resulting from calls to the device strategy routine, 98by examining the 99.Dv B_ERROR 100buffer flag and the 101.Va b_error 102field. 103Note that the actual transfer size may be less than requested by 104.Fa uio 105if the device signals an 106.Dq end of file 107condition. 108.Sh SEE ALSO 109.Xr read 2 , 110.Xr write 2 111.Sh HISTORY 112The 113.Xr physio 9 114manual page is originally from NetBSD with minor changes for applicability 115with FreeBSD. 116.Pp 117The physio(9) call has been completely re-written for providing higher 118I/O performance, and better paging performance. 119