device_probe9
Manage device's connection to a device driver
Part of device_probe_and_attach(9).
Usage
#include <sys/param.h>
#include <sys/bus.h>
int
device_attach(device_t dev);
int
device_detach(device_t dev);
int
device_probe(device_t dev);
int
device_probe_and_attach(device_t dev);
Overview
These functions manage the relationship between a device and device drivers.
device_probe() invokes the DEVICE_PROBE(9) method of each suitable driver and to find the driver with the best match for dev. If a matching driver is found, dev is set to the DS_ALIVE state and zero is returned. If dev is already attached to a device driver or has been disabled via device_disable(9), then it will not be probed and -1 is returned.
device_attach() fully attaches a device driver to dev. This function prints a description of the device and invokes the DEVICE_ATTACH(9) method. If the DEVICE_ATTACH(9) method succeeds, dev is set to the DS_ATTACHED state and zero is returned. If the DEVICE_ATTACH(9) method fails, BUS_CHILD_DETACHED(9) is called and an error value is returned.
If the device name and unit are disabled by a hint, device_attach() disables the device, demotes it to the DS_NOTPRESENT state, and returns ENXIO. The device retains its device name and unit and can be re-enabled via devctl(8).
device_probe_and_attach() is a wrapper function around device_probe() and device_attach() that fully initialises a device. If dev is already attached or disabled, device_probe_and_attach() leaves the device unchanged and returns zero. Otherwise, device_probe() is used to identify a device driver for dev and device_attach() finalizes attaching the driver to dev. Device drivers should generally use this function to initialize a device rather than direct calls to device_probe() and device_attach().
device_detach() detaches the device driver from dev. This function invokes the DEVICE_DETACH(9) method to tear down device driver state for dev. If the method fails, its error value is returned and dev remains attached. If the method succeeds, otherwise, BUS_CHILD_DETACHED(9) is called, the device is set to the DS_NOTPRESENT state, and zero is returned. If a device is busy, device_detach() fails with EBUSY and leaving dev unchanged.
Return values
Zero is returned on success, otherwise an appropriate error is returned. In addition, device_probe() returns -1 if dev is disabled or already attached.
Releases
Unchanged in 6 releases since FreeBSD 14.3-RELEASE.