175 lines
4.6 KiB
Groff
175 lines
4.6 KiB
Groff
.\"
|
|
.\" Copyright (c) 1997 Joerg Wunsch
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" 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.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\" "
|
|
.Dd February 2, 1997
|
|
.Os
|
|
.Dt UIO 9
|
|
.Sh NAME
|
|
.Nm uio ,
|
|
.Nm uiomove
|
|
.Nd device driver IO routines
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/uio.h>
|
|
.Pp
|
|
.Bd -literal
|
|
struct uio {
|
|
struct iovec *uio_iov;
|
|
int uio_iovcnt;
|
|
off_t uio_offset;
|
|
int uio_resid;
|
|
enum uio_seg uio_segflg;
|
|
enum uio_rw uio_rw;
|
|
struct proc *uio_procp;
|
|
};
|
|
.Ed
|
|
.Ft int
|
|
.Fn uiomove "caddr_t buf" "int howmuch" "struct uio *uiop"
|
|
.Sh DESCRIPTION
|
|
The function
|
|
.Fn uiomove
|
|
is used to handle transfer of data between buffers and IO vectors
|
|
that might possibly also cross the user/kernel space boundary.
|
|
.Pp
|
|
As a result of any
|
|
.Xr read 2 ,
|
|
.Xr write 2 ,
|
|
.Xr readv 2 ,
|
|
or
|
|
.Xr writev 2
|
|
system call that is being passed to a character-device driver, the
|
|
appropriate driver
|
|
.Em read
|
|
or
|
|
.Em write
|
|
entry will be called with a pointer to a
|
|
.Fa "struct uio"
|
|
being passed. The transfer request is encoded in this structure.
|
|
The driver itself should use
|
|
.Fn uiomove
|
|
to get at the data in this structure.
|
|
.Pp
|
|
The fields in the uio structure are:
|
|
.Bl -tag -width "uio_iovcntXXXX" -compact
|
|
.It Dv uio_iov
|
|
The array of IO vectors to be processed. In the case of scatter/gather
|
|
IO, this will be more than one vector.
|
|
.It Dv uio_iovcnt
|
|
The number of IO vectors present.
|
|
.It Dv uio_offset
|
|
The offset into the device.
|
|
.It Dv uio_resid
|
|
The number of bytes to process.
|
|
.It Dv uio_segflg
|
|
One of the following flags:
|
|
.Bl -tag -width "UIO_USERISPACEX" -compact
|
|
.It Dv UIO_USERSPACE
|
|
The IO vector points into a process's address space.
|
|
.It Dv UIO_SYSSPACE
|
|
The IO vector points into the kernel address space.
|
|
.It Dv UIO_USERISPACE
|
|
The IO vector points into the instruction area of a process's address
|
|
space.
|
|
.It Dv UIO_NOCOPY
|
|
Don't copy, already in object.
|
|
.El
|
|
.It Dv uio_rw uio_rw
|
|
The direction of the desired transfer, either
|
|
.Dv UIO_READ ,
|
|
or
|
|
.Dv UIO_WRITE .
|
|
.It Dv uio_procp
|
|
The pointer to a
|
|
.Li struct proc
|
|
for the associated process; used if
|
|
.Dv uio_segflg
|
|
indicates that the transfer is to be made from/to a process's address
|
|
space.
|
|
.El
|
|
.Sh EXAMPLES
|
|
The idea is that the driver maintains a private buffer for its data,
|
|
and processes the request in chunks of maximal the size of this
|
|
buffer. Note that the buffer handling below is very simplified and
|
|
won't work (the buffer pointer is not being advanced in case of a
|
|
partial read), it's just here to demonstrate the uio handling.
|
|
.Bd -literal
|
|
/* MIN() can be found there: */
|
|
#include <sys/param.h>
|
|
|
|
#define BUFSIZE 512
|
|
static char buffer[BUFSIZE];
|
|
|
|
static int data_available; /* amount of data that can be read */
|
|
|
|
static int
|
|
fooread(dev_t dev, struct uio *uio, int flag)
|
|
{
|
|
int rv, amnt;
|
|
|
|
while (uio->uio_resid > 0) {
|
|
if (data_available > 0) {
|
|
amnt = MIN(uio->uio_resid, data_available);
|
|
if ((rv = uiomove((caddr_t)buffer, amnt, uio))
|
|
!= 0)
|
|
goto error;
|
|
data_available -= amnt;
|
|
} else {
|
|
tsleep(...); /* wait for a better time */
|
|
}
|
|
}
|
|
return 0;
|
|
error:
|
|
/* do error cleanup here */
|
|
return rv;
|
|
}
|
|
|
|
.Ed
|
|
.Sh RETURN VALUES
|
|
.Fn uiomove
|
|
can return
|
|
.Er EFAULT
|
|
from the invoked
|
|
.Xr copyin 9
|
|
or
|
|
.Xr copyout 9
|
|
in case the transfer was to/from a process's address space.
|
|
.Sh SEE ALSO
|
|
.Xr read 2 ,
|
|
.Xr readv 2 ,
|
|
.Xr write 2 ,
|
|
.Xr writev 2 ,
|
|
.Xr copyin 9 ,
|
|
.Xr copyout 9 ,
|
|
.Xr sleep 9
|
|
.Sh HISTORY
|
|
The uio mechanism appeared in some early version of
|
|
.Ux .
|
|
.Sh AUTHORS
|
|
This man page has been written by
|
|
.ie t J\(:org Wunsch.
|
|
.el Joerg Wunsch.
|