VOLMGT_ACQUIRE(3VOLMGT) Volume Management Library Functions

NAME

volmgt_acquire - reserve removable media device

SYNOPSIS

cc [ flag ... ] file ... -lvolmgt [ library ... ]
#include <sys/types.h>

#include <volmgt.h>


int volmgt_acquire(char *dev, char *id, int ovr, char **err, pid_t *pidp);

DESCRIPTION

This function is obsolete. The management of removable media by the
Volume Management feature, including vold, has been replaced by
software that supports the Hardware Abstraction Layer (HAL).
Programmatic support for HAL is through the HAL APIs, which are
documented on the HAL web site. See hal(7). The return value of this
function is undefined.


The volmgt_acquire() routine reserves the removable media device
specified as dev. volmgt_acquire() operates in two different modes,
depending on whether or not volume management is running.


If volume management is running, volmgt_acquire() attempts to
reserve the removable media device specified as dev. Specify dev as
either a symbolic device name (for example, floppy0) or a physical
device pathname (for example, /dsk/unnamed_floppy).


If volume management is not running, volmgt_acquire() requires
callers to specify a physical device pathname for dev. Specifying
dev as a symbolic device name is not acceptable. In this mode,
volmgt_acquire() relies entirely on the major and minor numbers of
the device to determine whether or not the device is reserved.


If dev is free, volmgt_acquire() updates the internal device
reservation database with the caller's process id (pid) and the
specified id string.


If dev is reserved by another process, the reservation attempt
fails and volmgt_acquire():

o sets errno to EBUSY

o fills the caller's id value in the array pointed to by err

o fills in the pid to which the pointer pidp points with
the pid of the process which holds the reservation, if
the supplied pidp is non-zero


If the override ovr is non-zero, the call overrides the device
reservation.

RETURN VALUES

The return from this function is undefined.

ERRORS

The volmgt_acquire() routine fails if one or more of the following
are true:

EINVAL
One of the specified arguments is invalid or missing.


EBUSY
dev is already reserved by another process (and ovr was not
set to a non-zero value)

EXAMPLES

Example 1: Using volmgt_acquire()

In the following example, volume management is running and the first
floppy drive is reserved, accessed and released.


#include <volmgt.h>
char *errp;
if (!volmgt_acquire("floppy0", "FileMgr", 0, NULL,
&errp, NULL)) {
/* handle error case */
...
}
/* floppy acquired - now access it */
if (!volmgt_release("floppy0")) {
/* handle error case */
...
}

Example 2: Using volmgt_acquire() To Override A Lock On Another

Process


The following example shows how callers can override a lock on
another process using volmgt_acquire().


char *errp, buf[20];
int override = 0;
pid_t pid;
if (!volmgt_acquire("floppy0", "FileMgr", 0, &errp,
&pid)) {
if (errno == EBUSY) {
(void) printf("override %s (pid=%ld)?\n",
errp, pid); {
(void) fgets(buf, 20, stdin);
if (buf[0] == 'y') {
override++;
}
} else {
/* handle other errors */
...
}
}
if (override) {
if (!volmgt_acquire("floppy0", "FileMgr", 1,
&errp, NULL)) {
/* really give up this time! */
...
}
}

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
|Interface Stability | Obsolete |
+--------------------+-----------------+

SEE ALSO

free(3C), malloc(3C), volmgt_release(3VOLMGT), attributes(7), hal(7)

NOTES

When returning a string through err, volmgt_acquire() allocates a
memory area using malloc(3C). Use free(3C) to release the memory
area when no longer needed.


The ovr argument is intended to allow callers to override the current
device reservation. It is assumed that the calling application has
determined that the current reservation can safely be cleared. See
EXAMPLES.

March 8, 2007 VOLMGT_ACQUIRE(3VOLMGT)