Copyright 1989 AT&T
Copyright (c) 1997, Sun Microsystems, Inc. All Rights Reserved
The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
#include <sys/types.h> #include <sys/errno.h> #include <sys/open.h> #include <sys/uio.h> #include <sys/cred.h> #include <sys/ddi.h> #include <sys/sunddi.h> int prefixread(dev_t dev, struct uio *uio_p, cred_t *cred_p);
Architecture independent level 1 (DDI/DKI). This entry point is optional.
dev
Device number.
uio_p
Pointer to the uio(9S) structure that describes where the data is to be stored in user space.
cred_p
Pointer to the user credential structure for the I/O transaction.
The driver read() routine is called indirectly through cb_ops(9S) by the read(2) system call. The read() routine should check the validity of the minor number component of dev and the user credential structure pointed to by cred_p (if pertinent). The read() routine should supervise the data transfer into the user space described by the uio(9S) structure.
The read() routine should return 0 for success, or the appropriate error number.
Example 1 read() routine using physio()
The following is an example of a read() routine using physio(9F) to perform reads from a non-seekable device:
static int
xxread(dev_t dev, struct uio *uiop, cred_t *credp)
{
int rval;
offset_t off;
int instance;
xx_t xx;
instance = getminor(dev);
xx = ddi_get_soft_state(xxstate, instance);
if (xx == NULL)
return (ENXIO);
off = uiop->uio_loffset;
rval = physio(xxstrategy, NULL, dev, B_READ,
xxmin, uiop);
uiop->uio_loffset = off;
return (rval);
}
read(2), write(9E), physio(9F), cb_ops(9S), uio(9S)
Writing Device Drivers