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devctl(8) [freebsd man page]

DEVCTL(8)						    BSD System Manager's Manual 						 DEVCTL(8)

devctl -- device control utility SYNOPSIS
devctl attach device devctl detach [-f] device devctl disable [-f] device devctl enable device devctl suspend device devctl resume device devctl set driver [-f] device driver DESCRIPTION
The devctl utility adjusts the state of individual devices in the kernel's internal device hierarchy. Each invocation of devctl consists of a single command followed by command-specific arguments. Each command operates on a single device specified via the device argument. The device may be specified either as the name of an existing device or as a bus-specific address. More details on supported address formats can be found in devctl(3). The following commands are supported: attach device Force the kernel to re-probe the device. If a suitable driver is found, it is attached to the device. detach [-f] device Detach the device from its current device driver. If the -f flag is specified, the device driver will be detached even if the device is busy. disable [-f] device Disable a device. If the device is currently attached to a device driver, the device driver will be detached from the device, but the device will retain its current name. If the -f flag is specified, the device driver will be detached even if the device is busy. enable device Enable a device. The device will probe and attach if a suitable device driver is found. Note that this can re-enable a device dis- abled at boot time via a loader tunable. suspend device Suspend a device. This may include placing the device in a reduced power state. resume device Resume a suspended device to a fully working state. set driver [-f] device driver Force the device to use a device driver named driver. If the device is already attached to a device driver and the -f flag is speci- fied, the device will be detached from its current device driver before it is attached to the new device driver. If the device is already attached to a device driver and the -f flag is not specified, the device will not be changed. SEE ALSO
devctl(3), devinfo(8) HISTORY
The devctl utility first appeared in FreeBSD 11.0. BSD
February 5, 2015 BSD

Check Out this Related Man Page

DEVCTL(4)                                                  BSD Kernel Interfaces Manual                                                  DEVCTL(4)

devctl -- device event reporting and device control interface DESCRIPTION
The devctl device is used to report device events from the kernel. Future versions will allow for some device control as well. IMPLEMENTATION NOTES
This design allows only one reader for /dev/devctl. This is not desirable in the long run, but will get a lot of hair out of this implemen- tation. Maybe we should make this device a clonable device. Also note: we specifically do not attach a device to the 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 sysctl(3) interface that we have now might more properly be an ioctl(2) interface. SIGIO support is included in the driver. However, the author is not sure that the SIGIO support is done correctly. It was copied from a driver that had SIGIO support that likely has not been tested since FreeBSD 3.4 or FreeBSD 2.2.8! 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. The sysctl and boot parameter hw.bus.devctl_disable is used to disable devctl when no devd(8) is running. PROTOCOL
The devctl device uses an 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. Type Description ! A notify event, such as a link state change. + Device node in tree attached. - Device node in tree detached. ? Unknown device detected. Message Formats Except for the first character in the record, attach and detach messages have the same format. Tdev at parent on location Part Description T + or - dev The device name that was attached/detached. parent The device name of the parent bus that attached the device. location Bus specific location information. 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. 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. SEE ALSO
devd(8) BSD February 11, 2003 BSD
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