1.\" 2.\" Copyright (c) 2002 M. Warner Losh <imp@FreeBSD.org> 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. The name of the author may not be used to endorse or promote products 10.\" derived from this software without specific prior written permission. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.Dd September 21, 2020 25.Dt DEVCTL 4 26.Os 27.Sh NAME 28.Nm devctl 29.Nd "device event reporting and device control interface" 30.Sh SYNOPSIS 31The 32.Nm 33driver is automatically included in the kernel. 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 78.Va hw.bus.devctl_queue 79can be used to control queue length. 80It is set to 0 to disable 81.Nm 82when no 83.Xr devd 8 84is running. 85.Sh PROTOCOL 86The 87.Nm 88device 89uses an 90.Tn ASCII 91protocol. 92The driver returns one record at a time to its readers. 93Each record is terminated with a newline. 94The first character of the record is the event type. 95.Pp 96.Bl -column -compact "Type" "Description" 97.Em "Type Description" 98! A notify event, such as a link state change. 99+ Device node in tree attached. 100- Device node in tree detached. 101? Unknown device detected. 102.El 103.Ss Message Formats 104Except for the first character in the record, attach and detach 105messages have the same format. 106.Pp 107.D1 Ar T Ns Ar dev Li at Ar parent Li on Ar location 108.Pp 109.Bl -column -compact "location" "Description" 110.Em "Part Description" 111.It Ar T Ta "+ or -" 112.It Ar dev Ta "The device name that was attached/detached." 113.It Ar parent Ta "The device name of the parent bus that attached the device." 114.It Ar location Ta "Bus specific location information." 115.El 116.Pp 117The nomatch messages can be used to load devices driver. 118If you load a device driver, then one of two things can happen. 119If the device driver attaches to something, you will get a device 120attached message. 121If it does not, then nothing will happen. 122.Pp 123The attach and detach messages arrive after the event. 124This means one cannot use the attach message to load an alternate 125driver. 126The attach message driver has already claimed this device. 127One cannot use the detach messages to flush data to the device. 128The device is already gone. 129.Pp 130All values passed back are of the form 131.Sq key=value 132or 133.Sq key="value" . 134When the latter, the string 135.Dq value 136must have any internal backslashes doubled. 137It must also have any internal double quote characters 138.Sq " 139preceded by a backslash. 140All other characters should be passed through. 141.Sh SEE ALSO 142.Xr devd 8 143