NAME
hotplug
—
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 */ };
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 */ };
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 ALSO
HISTORY
The hotplug
device first appeared in
OpenBSD 3.6.
AUTHORS
The hotplug
driver was written by
Alexander Yurchenko
<grange@openbsd.org>.