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.\" $FreeBSD$ 26.\" 27.Dd March 26, 2014 28.Dt DEVCTL 4 29.Os 30.Sh NAME 31.Nm devctl 32.Nd "device event reporting and device control interface" 33.Sh DESCRIPTION 34The 35.Nm 36device is used to report device events from the kernel. 37Future versions will allow for some device control as well. 38.Sh IMPLEMENTATION NOTES 39This design allows only one reader for 40.Pa /dev/devctl . 41This is not desirable 42in the long run, but will get a lot of hair out of this implementation. 43Maybe we should make this device a clonable device. 44.Pp 45Also note: we specifically do not attach a device to the 46.Vt device_t 47tree 48to avoid potential chicken and egg problems. 49One could argue that all of this belongs to the root node. 50One could also further argue that the 51.Xr sysctl 3 52interface that we have now might more properly be an 53.Xr ioctl 2 54interface. 55.Pp 56.Dv SIGIO 57support is included in the driver. 58However, the author is not sure that the 59.Dv SIGIO 60support is done correctly. 61It was copied from a driver that had 62.Dv SIGIO 63support that likely has not been 64tested since 65.Fx 3.4 66or 67.Fx 2.2.8 ! 68.Pp 69The read channel for this device is used to report changes to 70userland in realtime. 71We return one record at a time. 72If you try to read this device a character at a time, you will lose 73the rest of the data. 74Listening programs are expected to cope. 75.Pp 76The sysctl 77.Va hw.bus.devctl_queue 78can be used to control queue length. It is set to 0 to disable 79.Nm 80when no 81.Xr devd 8 82is running. 83.Sh PROTOCOL 84The 85.Nm 86device 87uses an 88.Tn ASCII 89protocol. 90The driver returns one record at a time to its readers. 91Each record is terminated with a newline. 92The first character of the record is the event type. 93.Pp 94.Bl -column -compact "Type" "Description" 95.Em "Type Description" 96! A notify event, such as a link state change. 97+ Device node in tree attached. 98- Device node in tree detached. 99? Unknown device detected. 100.El 101.Ss Message Formats 102Except for the first character in the record, attach and detach 103messages have the same format. 104.Pp 105.D1 Ar T Ns Ar dev Li at Ar parent Li on Ar location 106.Pp 107.Bl -column -compact "location" "Description" 108.Em "Part Description" 109.It Ar T Ta "+ or -" 110.It Ar dev Ta "The device name that was attached/detached." 111.It Ar parent Ta "The device name of the parent bus that attached the device." 112.It Ar location Ta "Bus specific location information." 113.El 114.Pp 115The nomatch messages can be used to load devices driver. 116If you load a device driver, then one of two things can happen. 117If the device driver attaches to something, you will get a device 118attached message. 119If it does not, then nothing will happen. 120.Pp 121The attach and detach messages arrive after the event. 122This means one cannot use the attach message to load an alternate 123driver. 124The attach message driver has already claimed this device. 125One cannot use the detach messages to flush data to the device. 126The device is already gone. 127.Sh SEE ALSO 128.Xr devd 8 129