ee38f2e004
This fixes breakage resulting from r263754. Reported by: AN <andy@neu.net> Reviewed by: imp Pointy hat to: me
129 lines
4.1 KiB
Groff
129 lines
4.1 KiB
Groff
.\"
|
|
.\" Copyright (c) 2002 M. Warner Losh
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd March 26, 2014
|
|
.Dt DEVCTL 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm devctl
|
|
.Nd "device event reporting and device control interface"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
device is used to report device events from the kernel.
|
|
Future versions will allow for some device control as well.
|
|
.Sh IMPLEMENTATION NOTES
|
|
This design allows only one reader for
|
|
.Pa /dev/devctl .
|
|
This is not desirable
|
|
in the long run, but will get a lot of hair out of this implementation.
|
|
Maybe we should make this device a clonable device.
|
|
.Pp
|
|
Also note: we specifically do not attach a device to the
|
|
.Vt device_t
|
|
tree
|
|
to avoid potential chicken and egg problems.
|
|
One could argue that all of this belongs to the root node.
|
|
One could also further argue that the
|
|
.Xr sysctl 3
|
|
interface that we have now might more properly be an
|
|
.Xr ioctl 2
|
|
interface.
|
|
.Pp
|
|
.Dv SIGIO
|
|
support is included in the driver.
|
|
However, the author is not sure that the
|
|
.Dv SIGIO
|
|
support is done correctly.
|
|
It was copied from a driver that had
|
|
.Dv SIGIO
|
|
support that likely has not been
|
|
tested since
|
|
.Fx 3.4
|
|
or
|
|
.Fx 2.2.8 !
|
|
.Pp
|
|
The read channel for this device is used to report changes to
|
|
userland in realtime.
|
|
We return one record at a time.
|
|
If you try to read this device a character at a time, you will lose
|
|
the rest of the data.
|
|
Listening programs are expected to cope.
|
|
.Pp
|
|
The sysctl
|
|
.Va hw.bus.devctl_queue
|
|
can be used to control queue length. It is set to 0 to disable
|
|
.Nm
|
|
when no
|
|
.Xr devd 8
|
|
is running.
|
|
.Sh PROTOCOL
|
|
The
|
|
.Nm
|
|
device
|
|
uses an
|
|
.Tn ASCII
|
|
protocol.
|
|
The driver returns one record at a time to its readers.
|
|
Each record is terminated with a newline.
|
|
The first character of the record is the event type.
|
|
.Pp
|
|
.Bl -column -compact "Type" "Description"
|
|
.Em "Type Description"
|
|
! A notify event, such as a link state change.
|
|
+ Device node in tree attached.
|
|
- Device node in tree detached.
|
|
? Unknown device detected.
|
|
.El
|
|
.Ss Message Formats
|
|
Except for the first character in the record, attach and detach
|
|
messages have the same format.
|
|
.Pp
|
|
.D1 Ar T Ns Ar dev Li at Ar parent Li on Ar location
|
|
.Pp
|
|
.Bl -column -compact "location" "Description"
|
|
.Em "Part Description"
|
|
.It Ar T Ta "+ or -"
|
|
.It Ar dev Ta "The device name that was attached/detached."
|
|
.It Ar parent Ta "The device name of the parent bus that attached the device."
|
|
.It Ar location Ta "Bus specific location information."
|
|
.El
|
|
.Pp
|
|
The nomatch messages can be used to load devices driver.
|
|
If you load a device driver, then one of two things can happen.
|
|
If the device driver attaches to something, you will get a device
|
|
attached message.
|
|
If it does not, then nothing will happen.
|
|
.Pp
|
|
The attach and detach messages arrive after the event.
|
|
This means one cannot use the attach message to load an alternate
|
|
driver.
|
|
The attach message driver has already claimed this device.
|
|
One cannot use the detach messages to flush data to the device.
|
|
The device is already gone.
|
|
.Sh SEE ALSO
|
|
.Xr devd 8
|