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 FreeBSD 42.Sh NAME 43.Nm physio 44.Nd initiate I/O on raw devices 45.Sh SYNOPSIS 46.Fd #include <sys/param.h> 47.Fd #include <sys/systm.h> 48.Fd #include <sys/buf.h> 49.Ft int 50.Fn physio "dev_t dev" "struct uio *uio" "int ioflag" 51.Fc 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. It calls back on the 57provided 58.Fa strategy 59routine one or more times to complete the transfer described by 60.Fa uio . 61The maximum amount of data to transfer with each call to 62.Fa strategy 63is determined by the 64.Fa minphys 65routine. Since 66.Fa uio 67normally describes user space addresses, 68.Fn physio 69needs to lock the process into memory. This 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. In all cases, 75the buffer passed in 76.Fa bp 77is locked (marked as 78.Dq busy ) 79for the duration of the entire transfer. 80.Pp 81A break-down of the arguments follows: 82.Bl -tag -width indent 83.It Fa strategy 84The device strategy routine to call for each chunk of data to initiate 85device I/O. 86.It Fa bp 87The buffer to use with the strategy routine. The buffer flags will have 88.Dv B_BUSY , 89and 90.Dv B_PHYS 91set when passed to the strategy routine. If 92.Dv NULL , 93a buffer is allocated from a system pool. 94.It Fa dev 95The device number identifying the device to interact with. 96.It Fa flags 97Direction of transfer; the only valid settings are 98.Dv B_READ 99or 100.Dv B_WRITE . 101.It Fa minphys 102A device specific routine called to determine the maximum transfer size 103that the device's strategy routine can handle. 104.It Fa uio 105The description of the entire transfer as requested by the user process. 106Currently, the results of passing a 107.Fa uio 108structure with the 109.Sq uio_segflg 110set to anything other than 111.Dv UIO_USERSPACE , 112are undefined. 113.El 114.Pp 115.Sh RETURN VALUES 116If successful 117.Fn physio 118returns 0. 119.Er EFAULT 120is returned if the address range described by 121.Fa uio 122is not accessible by the requesting process. 123.Fn physio 124will return any error resulting from calls to the device strategy routine, 125by examining the 126.Dv B_ERROR 127buffer flag and the 128.Va b_error 129field. Note that the actual transfer size may be less than requested by 130.Fa uio 131if the device signals an 132.Dq end of file 133condition. 134.Sh SEE ALSO 135.Xr read 2 , 136.Xr write 2 137