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.Dd June 15, 1996 38.Dt PHYSIO 9 39.Os FreeBSD 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. It calls back on the 58provided 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. Since 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. In all cases, 76the buffer passed in 77.Fa bp 78is locked (marked as 79.Dq busy ) 80for the duration of the entire transfer. 81.Pp 82A break-down of the arguments follows: 83.Bl -tag -width indent 84.It Fa strategy 85The device strategy routine to call for each chunk of data to initiate 86device I/O. 87.It Fa bp 88The buffer to use with the strategy routine. The buffer flags will have 89.Dv B_BUSY , 90and 91.Dv B_PHYS 92set when passed to the strategy routine. If 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.Pp 116.Sh RETURN VALUES 117If successful 118.Fn physio 119returns 0. 120.Er EFAULT 121is returned if the address range described by 122.Fa uio 123is not accessible by the requesting process. 124.Fn physio 125will return any error resulting from calls to the device strategy routine, 126by examining the 127.Dv B_ERROR 128buffer flag and the 129.Va b_error 130field. Note 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