DEVCTL(4) BSD Kernel Interfaces Manual DEVCTL(4)NAME
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
Check Out this Related Man Page
DEVCTL(3) BSD Library Functions Manual DEVCTL(3)NAME
devctl, devctl_attach, devctl_detach, devctl_disable, devctl_enable, devctl_resume, devctl_suspend -- device control library
LIBRARY
library ``libdevctl''
SYNOPSIS
#include <devctl.h>
int
devctl_attach(const char *device);
int
devctl_detach(const char *device, bool force);
int
devctl_disable(const char *device, bool force_detach);
int
devctl_enable(const char *device);
int
devctl_resume(const char *device);
int
devctl_suspend(const char *device);
int
devctl_set_driver(const char *device, const char *driver, bool force);
DESCRIPTION
The devctl library adjusts the state of devices in the kernel's internal device hierarchy. Each control operation accepts a device argument
that identifies the device to adjust. The device may be specified as either the name of an existing device or as a bus-specific address.
The following bus-specific address formats are currently supported:
pcidomain:bus:slot:function
A PCI device with the specified domain, bus, slot, and function.
pcibus:slot:function
A PCI device in domain zero with the specified bus, slot, and function.
handle A device with an ACPI handle of handle. The handle must be specified as an absolute path and must begin with a ``''.
The devctl_attach() function probes a device and attaches a suitable device driver if one is found.
The devctl_detach() function detaches a device from its current device driver. The device is left detached until either a new driver for its
parent bus is loaded or the device is explicitly probed via devctl_attach(). If force is true, the current device driver will be detached
even if the device is busy.
The devctl_disable() function disables 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 force_detach is true, the current device driver will be detached even if
the device is busy. The device will remain disabled and detached until it is explicitly enabled via devctl_enable().
The devctl_enable() function re-enables a disabled device. The device will probe and attach if a suitable device driver is found.
The devctl_suspend() function suspends a device. This may include placing the device in a reduced power state, but any device driver cur-
rently attached to the device will remain attached.
The devctl_resume() function resumes a suspended device to a fully working state.
The devctl_set_driver() function attaches a device driver named driver to a device. If the device is already attached and force is false,
the request will fail. If the device is already attached and force is true, the device will be detached from its current device driver
before it is attached to the new device driver.
RETURN VALUES
The devctl_attach(), devctl_detach(), devctl_disable(), devctl_enable(), devctl_suspend(), devctl_resume(), and devctl_set_driver() functions
return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
ERRORS
In addition to specific errors noted below, all of the devctl functions may fail for any of the errors described in open(2) as well as:
[EINVAL] The device name is too long.
[ENOENT] No existing device matches the specified name or location.
[EPERM] The current process is not permitted to adjust the state of device.
The devctl_attach() function may fail if:
[EBUSY] The device is already attached.
[ENOMEM] An internal memory allocation request failed.
[ENXIO] The device is disabled.
[ENXIO] No suitable driver for the device could be found, or the driver failed to attach.
The devctl_detach() function may fail if:
[EBUSY] The current device driver for device is busy and cannot detach at this time. Note that some drivers may return this even
if force is true.
[ENXIO] The device is not attached to a driver.
[ENXIO] The current device driver for device does not support detaching.
The devctl_enable() function may fail if:
[EBUSY] The device is already enabled.
[ENOMEM] An internal memory allocation request failed.
[ENXIO] No suitable driver for the device could be found, or the driver failed to attach.
The devctl_disable() function may fail if:
[EBUSY] The current device driver for device is busy and cannot detach at this time. Note that some drivers may return this even
if force_detach is true.
[ENXIO] The device is already disabled.
[ENXIO] The current device driver for device does not support detaching.
The devctl_suspend() function may fail if:
[EBUSY] The device is already suspended.
[EINVAL] The device to be suspended is the root bus device.
The devctl_resume() function may fail if:
[EINVAL] The device is not suspended.
[EINVAL] The device to be resumed is the root bus device.
The devctl_set_driver() function may fail if:
[EBUSY] The device is currently attached to a device driver and force is false.
[EBUSY] The current device driver for device is busy and cannot detach at this time.
[EFAULT] The driver argument points outside the process' allocated address space.
[ENOENT] No device driver with the requested name exists.
[ENOMEM] An internal memory allocation request failed.
[ENXIO] The device is disabled.
[ENXIO] The new device driver failed to attach.
SEE ALSO devinfo(3), devstat(3), devctl(8)HISTORY
The devctl library first appeared in FreeBSD 11.0.
BUGS
If a device is suspended individually via devctl_suspend() and the entire machine is subsequently suspended, the device will be resumed when
the machine resumes.
BSD December 26, 2014 BSD