1.\" $OpenBSD: physio.9,v 1.3 2001/06/28 22:14:23 millert Exp $ 2.\" $NetBSD: physio.9,v 1.5 1999/03/16 00:40:47 garbled Exp $ 3.\" 4.\" Copyright (c) 1996 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Paul Kranenburg. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the NetBSD 21.\" Foundation, Inc. and its contributors. 22.\" 4. Neither the name of The NetBSD Foundation nor the names of its 23.\" contributors may be used to endorse or promote products derived 24.\" from this software without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36.\" POSSIBILITY OF SUCH DAMAGE. 37.\" 38.Dd June 15, 1996 39.Dt PHYSIO 9 40.Os 41.Sh NAME 42.Nm physio 43.Nd initiate I/O on raw devices 44.Sh SYNOPSIS 45.Ft int 46.Fo "physio" 47.Fa "void (*strategy)(struct buf *)" 48.Fa "struct buf *bp" 49.Fa "dev_t dev" 50.Fa "int flags" 51.Fa "void (*minphys)(struct buf *)" 52.Fa "struct uio *uio" 53.Fc 54.Sh DESCRIPTION 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 the 74.Fn uvm_vslock 75and 76.Fn uvm_vsunlock 77functions in 78.Xr uvm 9 ) . 79.Fn physio 80always awaits the completion of the entire requested transfer before 81returning, unless an error condition is detected earlier. 82In all cases, the buffer passed in 83.Fa bp 84is locked (marked as 85.Dq busy ) 86for the duration of the entire transfer. 87.Pp 88A break-down of the arguments follows: 89.Bl -tag -width indent 90.It Fa strategy 91The device strategy routine to call for each chunk of data to initiate 92device I/O. 93.It Fa bp 94The buffer to use with the strategy routine. 95The buffer flags will have 96.Dv B_BUSY , 97.Dv B_PHYS , 98and 99.Dv B_RAW 100set when passed to the strategy routine. 101If 102.Dv NULL , 103a buffer is allocated from a system pool. 104.It Fa dev 105The device number identifying the device to interact with. 106.It Fa flags 107Direction of transfer; the only valid settings are 108.Dv B_READ 109or 110.Dv B_WRITE . 111.It Fa minphys 112A device specific routine called to determine the maximum transfer size 113that the device's strategy routine can handle. 114.It Fa uio 115The description of the entire transfer as requested by the user process. 116Currently, the results of passing a 117.Fa uio 118structure with the 119.Sq uio_segflg 120set to anything other than 121.Dv UIO_USERSPACE , 122are undefined. 123.El 124.Sh RETURN VALUES 125If successful 126.Fn physio 127returns 0. 128.Er EFAULT 129is returned if the address range described by 130.Fa uio 131is not accessible by the requesting process. 132.Fn physio 133will return any error resulting from calls to the device strategy routine, 134by examining the 135.Dv B_ERROR 136buffer flag and the 137.Sq b_error 138field. 139Note that the actual transfer size may be less than requested by 140.Fa uio 141if the device signals an 142.Dq end of file 143condition. 144.Sh SEE ALSO 145.Xr read 2 , 146.Xr write 2 147