HOTPLUG(4) OpenBSD Programmer's Manual HOTPLUG(4)NAMEhotplug - devices hot plugging
SYNOPSIS
pseudo-device hotplug 1
#include <sys/types.h>
#include <sys/device.h>
#include <sys/hotplug.h>
DESCRIPTION
The hotplug pseudo-device passes device attachment and detachment events
to userland. When a device attaches or detaches, the corresponding event
is queued. The events can then be obtained from the queue through the
read(2) call on the /dev/hotplug device file. Once an event has been
read, it's deleted from the queue. The event queue has a limited size
and if it's full all new events will be dropped. Each event is described
with the following structure declared in the <sys/hotplug.h> header file:
struct hotplug_event {
int he_type; /* event type */
enum devclass he_devclass; /* device class */
char he_devname[16]; /* device name */
};
The he_type field describes the event type and can be either
HOTPLUG_DEVAT for device attachment or HOTPLUG_DEVDT for detachment. The
he_devclass field describes the device class. All device classes can be
found in the <sys/device.h> header file:
enum devclass {
DV_DULL, /* generic, no special info */
DV_CPU, /* CPU (carries resource utilization) */
DV_DISK, /* disk drive (label, etc) */
DV_IFNET, /* network interface */
DV_TAPE, /* tape device */
DV_TTY /* serial line interface */
};
The he_devname is a device name including unit number, e.g. sd1.
Only one structure can be read per call. If there are no events in the
queue, the read(2) call will block until an event appears.
DIAGNOSTICS
hotplug: event lost, queue full New events will be dropped until all
pending events have been read.
SEE ALSOread(2), hotplugd(8)HISTORY
The hotplug device first appeared in OpenBSD 3.6.
AUTHORS
The hotplug driver was written by Alexander Yurchenko
<grange@openbsd.org>.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9