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DEVICE_IDENTIFY – identify a device, register it



#include <sys/param.h>
#include <sys/bus.h>

DEVICE_IDENTIFY(driver_t *driver, device_t parent);


The identify function for a device is only needed for devices on buses that cannot identify their children independently, e.g.amp; the ISA bus. It is used to recognize the device (usually done by accessing non-ambiguous registers in the hardware) and to tell the kernel about it and thus creating a new device instance.

BUS_ADD_CHILD(9) is used to register the device as a child of the bus. The device's resources (such as IRQ and I/O ports) are registered with the kernel by calling bus_set_resource() for each resource (refer to bus_set_resource(9) for more information).

Since the device tree and the device driver tree are disjoint, the DEVICE_IDENTIFY() routine needs to take this into account. If you load and unload your device driver that has the identify routine, the child node has the potential for adding the same node multiple times unless specific measure are taken to preclude that possibility.


The following pseudo-code shows an example of a function that probes for a piece of hardware and registers it and its resource (an I/O port) with the kernel.
foo_identify(driver_t *driver, device_t parent)
        device_t child;

        retrieve_device_information;         if (devices matches one of your supported devices &&          not already in device tree) {                 child = BUS_ADD_CHILD(parent, 0, "foo", -1);                 bus_set_resource(child, SYS_RES_IOPORT, 0, FOO_IOADDR, 1);         } }


BUS_ADD_CHILD(9), bus_set_resource(9), device(9), device_add_child(9), DEVICE_ATTACH(9), DEVICE_DETACH(9), DEVICE_PROBE(9), DEVICE_SHUTDOWN(9)


This manual page was written by Alexander Langer <Mt alex@FreeBSD.org>.

DEVICE_IDENTIFY (9) January 15, 2017

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