1.\" 2.\" Copyright (c) 2002 M. Warner Losh 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. The name of the author may not be used to endorse or promote products 11.\" derived from this software without specific prior written permission. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD: src/share/man/man4/devctl.4,v 1.5 2006/08/04 07:56:32 yar Exp $ 26.\" $DragonFly: src/share/man/man4/devctl.4,v 1.2 2008/10/03 10:30:43 swildner Exp $ 27.\" 28.Dd October 2, 2008 29.Dt DEVCTL 4 30.Os 31.Sh NAME 32.Nm devctl 33.Nd "device event reporting and device control interface" 34.Sh DESCRIPTION 35The 36.Nm 37device is used to report device events from the kernel. 38Future versions will allow for some device control as well. 39.Sh IMPLEMENTATION NOTES 40This design allows only one reader for 41.Pa /dev/devctl . 42This is not desirable 43in the long run, but will get a lot of hair out of this implementation. 44Maybe we should make this device a clonable device. 45.Pp 46Also note: we specifically do not attach a device to the 47.Vt device_t 48tree 49to avoid potential chicken and egg problems. 50One could argue that all of this belongs to the root node. 51One could also further argue that the 52.Xr sysctl 3 53interface that we have now might more properly be an 54.Xr ioctl 2 55interface. 56.Pp 57.Dv SIGIO 58support is included in the driver. 59However, the author is not sure that the 60.Dv SIGIO 61support is done correctly. 62It was copied from a driver that had 63.Dv SIGIO 64support that likely has not been 65tested since 66.Fx 3.4 67or 68.Fx 2.2.8 ! 69.Pp 70The read channel for this device is used to report changes to 71userland in realtime. 72We return one record at a time. 73If you try to read this device a character at a time, you will lose 74the rest of the data. 75Listening programs are expected to cope. 76.Pp 77The sysctl and boot parameter 78.Va hw.bus.devctl_disable 79is used to disable 80.Nm 81when no 82.Xr devd 8 83is running. 84.Sh PROTOCOL 85The 86.Nm 87device 88uses an 89.Tn ASCII 90protocol. 91The driver returns one record at a time to its readers. 92Each record is terminated with a newline. 93The first character of the record is the event type. 94.Pp 95.Bl -column -compact "Type" "Description" 96.Em "Type Description" 97! A notify event, such as a link state change. 98+ Device node in tree attached. 99- Device node in tree detached. 100? Unknown device detected. 101.El 102.Ss Message Formats 103Except for the first character in the record, attach and detach 104messages have the same format. 105.Pp 106.D1 Ar T Ns Ar dev Li at Ar parent Li on Ar location 107.Pp 108.Bl -column -compact "location" "Description" 109.Em "Part Description" 110.It Ar T Ta "+ or -" 111.It Ar dev Ta "The device name that was attached/detached." 112.It Ar parent Ta "The device name of the parent bus that attached the device." 113.It Ar location Ta "Bus specific location information." 114.El 115.Pp 116The nomatch messages can be used to load devices driver. 117If you load a device driver, then one of two things can happen. 118If the device driver attaches to something, you will get a device 119attached message. 120If it does not, then nothing will happen. 121.Pp 122The attach and detach messages arrive after the event. 123This means one cannot use the attach message to load an alternate 124driver. 125The attach message driver has already claimed this device. 126One cannot use the detach messages to flush data to the device. 127The device is already gone. 128.Sh SEE ALSO 129.Xr devd 8 130