1.\" $NetBSD: physio.9,v 1.11 2010/04/13 10:06:43 jruoho 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 April 13, 2010 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 51.Tn I/O 52on a user process buffer. 53It calls back on the provided 54.Fa strategy 55routine one or more times to complete the transfer described by 56.Fa uio . 57The maximum amount of data to transfer with each call to 58.Fa strategy 59is determined by the 60.Fa minphys 61routine. 62.Pp 63Since 64.Fa uio 65normally describes user space addresses, 66.Fn physio 67needs to lock the appropriate data area into memory before each transaction 68with 69.Fa strategy 70(see 71.Xr uvm_vslock 9 72and 73.Xr uvm_vsunlock 9 ) . 74The 75.Fn physio 76function always awaits the completion of the entire requested transfer before 77returning, unless an error condition is detected earlier. 78In all cases, the 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 "strategy " 86.It Fa strategy 87The device strategy routine to call for each chunk of data to initiate 88device 89.Tn I/O . 90.It Fa bp 91The buffer to use with the strategy routine. 92The buffer flags will have 93.Dv B_BUSY , 94.Dv B_PHYS , 95and 96.Dv B_RAW 97set when passed to the strategy routine. 98If 99.Dv NULL , 100a buffer is allocated from a system pool. 101.It Fa dev 102The device number identifying the device to interact with. 103.It Fa flags 104Direction of transfer; the only valid settings are 105.Dv B_READ 106or 107.Dv B_WRITE . 108.It Fa minphys 109A device specific routine called to determine the maximum transfer size 110that the device's strategy routine can handle. 111.It Fa uio 112The description of the entire transfer as requested by the user process. 113Currently, the results of passing a 114.Fa uio 115structure with the 116.Sq uio_segflg 117set to anything other than 118.Dv UIO_USERSPACE , 119are undefined. 120.El 121.Sh RETURN VALUES 122If successful 123.Fn physio 124returns 0. 125.Er EFAULT 126is returned if the address range described by 127.Fa uio 128is not accessible by the requesting process. 129.Fn physio 130will return any error resulting from calls to the device strategy routine, 131by examining the 132.Dv B_ERROR 133buffer flag and the 134.Sq b_error 135field. 136Note that the actual transfer size may be less than requested by 137.Fa uio 138if the device signals an 139.Dq end of file 140condition. 141.Sh SEE ALSO 142.Xr read 2 , 143.Xr write 2 144