1.\" $NetBSD: physio.9,v 1.9 2001/06/21 12:13:36 wiz 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 FOUNDATION OR CONTRIBUTORS 29.\" BE 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.Dd June 15, 1996 38.Dt PHYSIO 9 39.Os 40.Sh NAME 41.Nm physio 42.Nd initiate I/O on raw devices 43.Sh SYNOPSIS 44.Ft int 45.Fo "physio" 46.Fa "(*strategy)(struct buf *)" 47.Fa "struct buf *bp" 48.Fa "dev_t dev" 49.Fa "int flags" 50.Fa "(*minphys)(struct buf *)" 51.Fa "struct uio *uio" 52.Fc 53.Sh DESCRIPTION 54The 55.Fn physio 56is a helper function typically called from character device read and write 57routines to start I/O on a user process buffer. 58It calls back on the provided 59.Fa strategy 60routine one or more times to complete the transfer described by 61.Fa uio . 62The maximum amount of data to transfer with each call to 63.Fa strategy 64is determined by the 65.Fa minphys 66routine. 67Since 68.Fa uio 69normally describes user space addresses, 70.Fn physio 71needs to lock the appropriate data area into memory before each transaction 72with 73.Fa strategy ( see 74.Xr uvm_vslock 9 75and 76.Xr uvm_vsunlock 9 ) . 77.Fn physio 78always awaits the completion of the entire requested transfer before 79returning, unless an error condition is detected earlier. 80In all cases, the buffer passed in 81.Fa bp 82is locked (marked as 83.Dq busy ) 84for the duration of the entire transfer. 85.Pp 86A break-down of the arguments follows: 87.Bl -tag -width indent 88.It Fa strategy 89The device strategy routine to call for each chunk of data to initiate 90device I/O. 91.It Fa bp 92The buffer to use with the strategy routine. 93The buffer flags will have 94.Dv B_BUSY , 95.Dv B_PHYS , 96and 97.Dv B_RAW 98set when passed to the strategy routine. 99If 100.Dv NULL , 101a buffer is allocated from a system pool. 102.It Fa dev 103The device number identifying the device to interact with. 104.It Fa flags 105Direction of transfer; the only valid settings are 106.Dv B_READ 107or 108.Dv B_WRITE . 109.It Fa minphys 110A device specific routine called to determine the maximum transfer size 111that the device's strategy routine can handle. 112.It Fa uio 113The description of the entire transfer as requested by the user process. 114Currently, the results of passing a 115.Fa uio 116structure with the 117.Sq uio_segflg 118set to anything other than 119.Dv UIO_USERSPACE , 120are undefined. 121.El 122.Sh RETURN VALUES 123If successful 124.Fn physio 125returns 0. 126.Er EFAULT 127is returned if the address range described by 128.Fa uio 129is not accessible by the requesting process. 130.Fn physio 131will return any error resulting from calls to the device strategy routine, 132by examining the 133.Dv B_ERROR 134buffer flag and the 135.Sq b_error 136field. 137Note that the actual transfer size may be less than requested by 138.Fa uio 139if the device signals an 140.Dq end of file 141condition. 142.Sh SEE ALSO 143.Xr read 2 , 144.Xr write 2 145