Copyright (c) 2004 Alexander Yurchenko <grange@openbsd.org>
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.Dd $Mdocdate: January 21 2014 $ .Dt HOTPLUG 4 .Os .Sh NAME .Nm hotplug .Nd devices hot plugging .Sh SYNOPSIS .Cd "pseudo-device hotplug 1"
p n sys/types.h n sys/device.h n sys/hotplug.h .Sh DESCRIPTION The .Nm 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 .Xr read 2 call on the
a /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 n sys/hotplug.h header file: d -literal -offset indent struct hotplug_event { int he_type; /* event type */ enum devclass he_devclass; /* device class */ char he_devname[16]; /* device name */ }; .Ed The .Va he_type field describes the event type and can be either .Dv HOTPLUG_DEVAT for device attachment or .Dv HOTPLUG_DEVDT for detachment. The .Va he_devclass field describes the device class. All device classes can be found in the n sys/device.h header file: d -literal -offset indent 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 */ }; .Ed The .Va he_devname is a device name including unit number, e.g.\&
a sd1 .
p Only one structure can be read per call. If there are no events in the queue, the .Xr read 2 call will block until an event appears. .Sh DIAGNOSTICS l -diag t "hotplug: event lost, queue full" New events will be dropped until all pending events have been read. .El .Sh SEE ALSO .Xr read 2 , .Xr hotplugd 8 .Sh HISTORY The .Nm device first appeared in .Ox 3.6 . .Sh AUTHORS The .Nm driver was written by .An Alexander Yurchenko Aq Mt grange@openbsd.org .