Copyright (c) 1996 The NetBSD Foundation, Inc.
All rights reserved.
This code is derived from software contributed to The NetBSD Foundation
by Paul Kranenburg.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the NetBSD
Foundation, Inc. and its contributors.
4. Neither the name of The NetBSD Foundation nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
$FreeBSD: head/share/man/man9/physio.9 139592 2005-01-02 18:20:29Z krion $
.Dd July 8, 2004 .Dt PHYSIO 9 .Os .Sh NAME .Nm physio .Nd initiate I/O on raw devices .Sh SYNOPSIS n sys/param.h n sys/systm.h n sys/bio.h n sys/buf.h .Ft int .Fn physio "dev_t dev" "struct uio *uio" "int ioflag" .Sh DESCRIPTION The .Fn physio is a helper function typically called from character device .Fn read and .Fn write routines to start I/O on a user process buffer. The maximum amount of data to transfer with each call is determined by .Fa dev->si_iosize_max . The .Fn physio call converts the I/O request into a .Fn strategy request and passes the new request to the driver's .Fn strategy routine for processing.
p Since .Fa uio normally describes user space addresses, .Fn physio needs to lock the those pages into memory. This is done by calling .Fn vmapbuf for the appropriate pages. .Fn physio always awaits the completion of the entire requested transfer before returning, unless an error condition is detected earlier.
p A break-down of the arguments follows: l -tag -width indent t Fa dev The device number identifying the device to interact with. t Fa uio The description of the entire transfer as requested by the user process. Currently, the results of passing a .Fa uio structure with the .Va uio_segflg set to anything other than .Dv UIO_USERSPACE are undefined. t Fa ioflag The ioflag argument from the .Fn read or .Fn write function calling .Fn physio . .El .Sh RETURN VALUES If successful .Fn physio returns 0. .Er EFAULT is returned if the address range described by .Fa uio is not accessible by the requesting process. .Fn physio will return any error resulting from calls to the device strategy routine, by examining the .Dv B_ERROR buffer flag and the .Va b_error field. Note that the actual transfer size may be less than requested by .Fa uio if the device signals an .Dq "end of file" condition. .Sh SEE ALSO .Xr read 2 , .Xr write 2 .Sh HISTORY The .Nm manual page is originally from .Nx with minor changes for applicability with .Fx .
p The .Nm call has been completely re-written for providing higher I/O and paging performance.