142 lines
4.4 KiB
Groff
142 lines
4.4 KiB
Groff
.\" $NetBSD: physio.9,v 1.2 1996/11/11 00:05:12 lukem Exp $
|
|
.\"
|
|
.\" 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.
|
|
.\"
|
|
.Dd June 15, 1996
|
|
.Dt PHYSIO 9
|
|
.Os NetBSD
|
|
.Sh NAME
|
|
.Nm physio
|
|
.Nd initiate I/O on raw devices
|
|
.Sh SYNOPSIS
|
|
.Ft int
|
|
.Fo "physio"
|
|
.Fa "(*strategy)(struct buf *)"
|
|
.Fa "struct buf *bp"
|
|
.Fa "dev_t dev"
|
|
.Fa "int flags"
|
|
.Fa "(*minphys)(struct buf *)"
|
|
.Fa "struct uio *uio"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn physio
|
|
is a helper function typically called from character device read and write
|
|
routines to start I/O on a user process buffer. It calls back on the
|
|
provided
|
|
.Fa strategy
|
|
routine one or more times to complete the transfer described by
|
|
.Fa uio .
|
|
The maximum amount of data to transfer with each call to
|
|
.Fa strategy
|
|
is determined by the
|
|
.Fa minphys
|
|
routine. Since
|
|
.Fa uio
|
|
normally describes user space addresses,
|
|
.Fn physio
|
|
needs to lock the appropriate data area into memory before each transaction
|
|
with
|
|
.Fa strategy ( see
|
|
.Xr vslock 9
|
|
and
|
|
.Xr vsunlock 9 ).
|
|
.Fn physio
|
|
always awaits the completion of the entire requested transfer before
|
|
returning, unless an error condition is detected earlier. In all cases,
|
|
the buffer passed in
|
|
.Fa bp
|
|
is locked (marked as
|
|
.Dq busy )
|
|
for the duration of the entire transfer.
|
|
.Pp
|
|
A break-down of the arguments follows:
|
|
.Bl -tag -width indent
|
|
.It Fa strategy
|
|
The device strategy routine to call for each chunk of data to initiate
|
|
device I/O.
|
|
.It Fa bp
|
|
The buffer to use with the strategy routine. The buffer flags will have
|
|
.Dv B_BUSY ,
|
|
.Dv B_PHYS ,
|
|
and
|
|
.Dv B_RAW
|
|
set when passed to the strategy routine. If
|
|
.Dv NULL ,
|
|
a buffer is allocated from a system pool.
|
|
.It Fa dev
|
|
The device number identifying the device to interact with.
|
|
.It Fa flags
|
|
Direction of transfer; the only valid settings are
|
|
.Dv B_READ
|
|
or
|
|
.Dv B_WRITE .
|
|
.It Fa minphys
|
|
A device specific routine called to determine the maximum transfer size
|
|
that the device's strategy rouinte can handle.
|
|
.It 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
|
|
.Sq uio_segflg
|
|
set to anything other than
|
|
.Dv UIO_USERSPACE ,
|
|
are undefined.
|
|
.El
|
|
.Pp
|
|
.Sh RETURN VALUES
|
|
If successful
|
|
.Fn physio
|
|
returns 0.
|
|
.Er EFAULT
|
|
is returned if the address range described by
|
|
.Fa uio
|
|
is not accessable 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
|
|
.Sq 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
|