1.\" $NetBSD: physio.9,v 1.10 2008/04/30 13:10:58 martin 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.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd June 15, 1996 31.Dt PHYSIO 9 32.Os 33.Sh NAME 34.Nm physio 35.Nd initiate I/O on raw devices 36.Sh SYNOPSIS 37.Ft int 38.Fo "physio" 39.Fa "(*strategy)(struct buf *)" 40.Fa "struct buf *bp" 41.Fa "dev_t dev" 42.Fa "int flags" 43.Fa "(*minphys)(struct buf *)" 44.Fa "struct uio *uio" 45.Fc 46.Sh DESCRIPTION 47The 48.Fn physio 49is a helper function typically called from character device read and write 50routines to start I/O on a user process buffer. 51It calls back on the provided 52.Fa strategy 53routine one or more times to complete the transfer described by 54.Fa uio . 55The maximum amount of data to transfer with each call to 56.Fa strategy 57is determined by the 58.Fa minphys 59routine. 60Since 61.Fa uio 62normally describes user space addresses, 63.Fn physio 64needs to lock the appropriate data area into memory before each transaction 65with 66.Fa strategy ( see 67.Xr uvm_vslock 9 68and 69.Xr uvm_vsunlock 9 ) . 70.Fn physio 71always awaits the completion of the entire requested transfer before 72returning, unless an error condition is detected earlier. 73In all cases, the buffer passed in 74.Fa bp 75is locked (marked as 76.Dq busy ) 77for the duration of the entire transfer. 78.Pp 79A break-down of the arguments follows: 80.Bl -tag -width indent 81.It Fa strategy 82The device strategy routine to call for each chunk of data to initiate 83device I/O. 84.It Fa bp 85The buffer to use with the strategy routine. 86The buffer flags will have 87.Dv B_BUSY , 88.Dv B_PHYS , 89and 90.Dv B_RAW 91set when passed to the strategy routine. 92If 93.Dv NULL , 94a buffer is allocated from a system pool. 95.It Fa dev 96The device number identifying the device to interact with. 97.It Fa flags 98Direction of transfer; the only valid settings are 99.Dv B_READ 100or 101.Dv B_WRITE . 102.It Fa minphys 103A device specific routine called to determine the maximum transfer size 104that the device's strategy routine can handle. 105.It Fa uio 106The description of the entire transfer as requested by the user process. 107Currently, the results of passing a 108.Fa uio 109structure with the 110.Sq uio_segflg 111set to anything other than 112.Dv UIO_USERSPACE , 113are undefined. 114.El 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.Sq b_error 129field. 130Note that the actual transfer size may be less than requested by 131.Fa uio 132if the device signals an 133.Dq end of file 134condition. 135.Sh SEE ALSO 136.Xr read 2 , 137.Xr write 2 138