VOLMGT_ACQUIRE(3VOLMGT)VOLMGT_ACQUIRE(3VOLMGT)NAMEvolmgt_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This function is obsolete.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Volume Management feature, including vold, has been replaced by soft‐
ware 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(5). The return value of this function is unde‐
fined.
The volmgt_acquire() routine reserves the removable media device spec‐
ified 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 path‐
name (for example, /dsk/unnamed_floppy).
If volume management is not running, volmgt_acquire() requires call‐
ers 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 reserva‐
tion 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 reser‐
vation.
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(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│MT-Level │ MT-Safe │
├────────────────────┼─────────────────┤
│Interface Stability │ Obsolete │
└────────────────────┴─────────────────┘
SEE ALSOfree(3C), malloc(3C), volmgt_release(3VOLMGT), attributes(5), hal(5)NOTES
When returning a string through err, volmgt_acquire() allocates a mem‐
ory 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.
Mar 8, 2007 VOLMGT_ACQUIRE(3VOLMGT)
