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DEVCTL(3) Library Functions Manual DEVCTL(3)

devctl, devctl_attach, devctl_clear_driver, devctl_delete, devctl_detach, devctl_disable, devctl_enable, devctl_freeze, devctl_getpath, devctl_rescan, devctl_reset, devctl_resume, devctl_set_driver, devctl_suspend, devctl_thaw — device control library

Device Control Library (libdevctl, -ldevctl)

#include <devctl.h>

int
devctl_attach(const char *device);

int
devctl_clear_driver(const char *device, bool force);

int
devctl_delete(const char *device, bool force);

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_freeze(void);

int
devctl_getpath(const char *device, const char *locator, char **buffer);

int
devctl_rescan(const char *device);

int
devctl_reset(const char *device, bool detach);

int
devctl_resume(const char *device);

int
devctl_set_driver(const char *device, const char *driver, bool force);

int
devctl_suspend(const char *device);

int
devctl_thaw(void);

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:

domain:bus:slot:function
A PCI device with the specified domain, bus, slot, and function.
bus: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 () function probes a device and attaches a suitable device driver if one is found.

The () 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 () function deletes a device from the device tree. No If force is true, the device is deleted even if the device is physically present.

The () 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 () function re-enables a disabled device. The device will probe and attach if a suitable device driver is found.

The () function suspends a device. This may include placing the device in a reduced power state, but any device driver currently attached to the device will remain attached.

The () function resumes a suspended device to a fully working state.

The () 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.

The () function resets a device so that it can be attached to any valid device driver rather than only drivers with a previously specified name. This function is used to undo a previous call to devctl_set_driver(). 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. After the device's name is reset, it is reprobed and attached to a suitable device driver if one is found.

The () function rescans a bus device checking for devices that have been added or removed.

The () retrieves the path to the device from the kernel using the locator method to construct the path. The buffer pointer is updated with an allocated buffer that must be freed with free(3).

The () function freezes probe and attach processing initiated in response to drivers being loaded.

The () function resumes (thaws the freeze) probe and attach processing initiated in response to drivers being loaded.

The () function resets the specified device using bus-specific reset method. The detach argument, if true, specifies that the device driver is detached before the reset, and re-attached afterwards. If false, the device is suspended before the reset, and resumed after.

The devctl_attach(), devctl_clear_driver(), devctl_delete(), devctl_detach(), devctl_disable(), devctl_enable(), devctl_suspend(), devctl_rescan(), 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.

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:

[]
The device name is too long.
[]
No existing device matches the specified name or location.
[]
The current process is not permitted to adjust the state of device.

The devctl_attach() function may fail if:

[]
The device is already attached.
[]
An internal memory allocation request failed.
[]
The device is disabled.
[]
No suitable driver for the device could be found, or the driver failed to attach.

The devctl_detach() function may fail if:

[]
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.
[]
The device is not attached to a driver.
[]
The current device driver for device does not support detaching.

The devctl_enable() function may fail if:

[]
The device is already enabled.
[]
An internal memory allocation request failed.
[]
No suitable driver for the device could be found, or the driver failed to attach.

The devctl_disable() function may fail if:

[]
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.
[]
The device is already disabled.
[]
The current device driver for device does not support detaching.

The devctl_suspend() function may fail if:

[]
The device is already suspended.
[]
The device to be suspended is the root bus device.

The devctl_resume() function may fail if:

[]
The device is not suspended.
[]
The device to be resumed is the root bus device.

The devctl_set_driver() function may fail if:

[]
The device is currently attached to a device driver and force is false.
[]
The current device driver for device is busy and cannot detach at this time.
[]
The driver argument points outside the process' allocated address space.
[]
No device driver with the requested name exists.
[]
An internal memory allocation request failed.
[]
The device is disabled.
[]
The new device driver failed to attach.

The devctl_clear_driver() function may fail if:

[]
The device is currently attached to a device driver and force is false.
[]
The current device driver for device is busy and cannot detach at this time.
[]
The device is not configured for a specific device driver name.
[]
The device driver chosen after reprobing failed to attach.

The devctl_rescan() function may fail if:

[]
The device is not attached to a driver.
[]
The bus driver does not support rescanning.

The devctl_delete() function may fail if:

[]
The device is physically present and force is false.
[]
dev is the root device of the device tree.

The devctl_reset() function may fail if:

[]
The bus does not implement the reset method.
[]
The device failed to respond after the reset in the time limits specific to the bus.
The devctl_reset() function may also return errors caused by the attach, detach, suspend, and resume methods of the device driver.

devinfo(3), devstat(3), devctl(8)

The devctl library first appeared in FreeBSD 10.3.

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.

Similarly, if the device is suspended, and devctl_reset() is called on the device with detach set to false, the device is resumed by the devctl_reset() call. Or, if the driver for the device is detached manually, and devctl_reset() is called on the device with detach set to true, device reset re-attaches the driver.

April 4, 2019 dev