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: src/share/man/man9/physio.9,v 1.6.2.4 2001/12/17 11:30:18 ru Exp $ 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/buf.h 49.Ft int 50.Fn physio "dev_t dev" "struct uio *uio" "int ioflag" 51.Sh DESCRIPTION 52The 53.Fn physio 54is a helper function typically called from character device read and write 55routines to start I/O on a user process buffer. 56It 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. 66Since 67.Fa uio 68normally describes user space addresses, 69.Fn physio 70needs to lock the process into memory. This is done by setting the 71.Dv P_PHYSIO 72flag on the process. 73.Fn physio 74always awaits the completion of the entire requested transfer before 75returning, unless an error condition is detected earlier. 76In all cases, 77the buffer passed in 78.Fa bp 79is locked (marked as 80.Dq busy ) 81for the duration of the entire transfer. 82.Pp 83A break-down of the arguments follows: 84.Bl -tag -width indent 85.It Fa strategy 86The device strategy routine to call for each chunk of data to initiate 87device I/O. 88.It Fa bp 89The buffer to use with the strategy routine. 90The buffer flags will have 91.Dv B_BUSY , 92and 93.Dv B_PHYS 94set when passed to the strategy routine. 95If 96.Dv NULL , 97a buffer is allocated from a system pool. 98.It Fa dev 99The device number identifying the device to interact with. 100.It Fa flags 101Direction of transfer; the only valid settings are 102.Dv B_READ 103or 104.Dv B_WRITE . 105.It Fa minphys 106A device specific routine called to determine the maximum transfer size 107that the device's strategy routine can handle. 108.It Fa uio 109The description of the entire transfer as requested by the user process. 110Currently, the results of passing a 111.Fa uio 112structure with the 113.Sq uio_segflg 114set to anything other than 115.Dv UIO_USERSPACE , 116are undefined. 117.El 118.Sh RETURN VALUES 119If successful 120.Fn physio 121returns 0. 122.Er EFAULT 123is returned if the address range described by 124.Fa uio 125is not accessible by the requesting process. 126.Fn physio 127will return any error resulting from calls to the device strategy routine, 128by examining the 129.Dv B_ERROR 130buffer flag and the 131.Va b_error 132field. 133Note that the actual transfer size may be less than requested by 134.Fa uio 135if the device signals an 136.Dq end of file 137condition. 138.Sh SEE ALSO 139.Xr read 2 , 140.Xr write 2 141