.\" $OpenBSD: hotplug.4,v 1.1 2004/05/30 08:35:19 grange Exp $ .\" .\" Copyright (c) 2004 Alexander Yurchenko .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .Dd March 30, 2004 .Dt HOTPLUG 4 .Os .Sh NAME .Nm hotplug .Nd devices hot plugging .Sh SYNOPSIS .Cd "pseudo-device hotplug 1" .Pp .Fd #include .Fd #include .Fd #include .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 .Pa /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 .Aq Pa sys/hotplug.h header file: .Bd -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 .Aq Pa sys/device.h header file: .Bd -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.\& .Pa sd1 . .Pp 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 .Bl -diag .It "hotplug: event lost, queue full" New events will be dropped until pending events aren't 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 grange@openbsd.org .