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.\" $FreeBSD$ 38.\" 39.Dd June 15, 1996 40.Dt PHYSIO 9 41.Os FreeBSD 42.Sh NAME 43.Nm physio 44.Nd initiate I/O on raw devices 45.Sh SYNOPSIS 46.Fd #include <sys/param.h> 47.Fd #include <sys/buf.h> 48.Ft int 49.Fo physio 50.Fa "void (*strategy)(struct buf *)" 51.Fa "struct buf *bp" 52.Fa "dev_t dev" 53.Fa "int flags" 54.Fa "u_int (*minphys)(struct buf *)" 55.Fa "struct uio *uio" 56.Fc 57.Sh DESCRIPTION 58The 59.Fn physio 60is a helper function typically called from character device read and write 61routines to start I/O on a user process buffer. It calls back on the 62provided 63.Fa strategy 64routine one or more times to complete the transfer described by 65.Fa uio . 66The maximum amount of data to transfer with each call to 67.Fa strategy 68is determined by the 69.Fa minphys 70routine. Since 71.Fa uio 72normally describes user space addresses, 73.Fn physio 74needs to lock the process into memory. This is done by setting the 75.Dv P_PHYSIO 76flag on the process. 77.Fn physio 78always awaits the completion of the entire requested transfer before 79returning, unless an error condition is detected earlier. In all cases, 80the 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. The buffer flags will have 93.Dv B_BUSY , 94and 95.Dv B_PHYS 96set when passed to the strategy routine. If 97.Dv NULL , 98a buffer is allocated from a system pool. 99.It Fa dev 100The device number identifying the device to interact with. 101.It Fa flags 102Direction of transfer; the only valid settings are 103.Dv B_READ 104or 105.Dv B_WRITE . 106.It Fa minphys 107A device specific routine called to determine the maximum transfer size 108that the device's strategy routine can handle. 109.It Fa uio 110The description of the entire transfer as requested by the user process. 111Currently, the results of passing a 112.Fa uio 113structure with the 114.Sq uio_segflg 115set to anything other than 116.Dv UIO_USERSPACE , 117are undefined. 118.El 119.Pp 120.Sh RETURN VALUES 121If successful 122.Fn physio 123returns 0. 124.Er EFAULT 125is returned if the address range described by 126.Fa uio 127is not accessible by the requesting process. 128.Fn physio 129will return any error resulting from calls to the device strategy routine, 130by examining the 131.Dv B_ERROR 132buffer flag and the 133.Va b_error 134field. Note that the actual transfer size may be less than requested by 135.Fa uio 136if the device signals an 137.Dq end of file 138condition. 139.Sh SEE ALSO 140.Xr read 2 , 141.Xr write 2 142