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