DEVICE_IDENTIFY (9)
Leading comments
Copyright (c) 2001 Alexander Langer All rights reserved. This program is free software. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaim...
NAME
DEVICE_IDENTIFY - identify a device, register itSYNOPSIS
In sys/param.h In sys/bus.h Ft void Fn DEVICE_IDENTIFY driver_t *driver device_t parentDESCRIPTION
The identify function for a device is only needed for devices on busses that cannot identify their children independently, e.g. 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_CHILD9 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 Fn bus_set_resource for each resource (refer to bus_set_resource9 for more information).
Since the device tree and the device driver tree are disjoint, the Fn 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.
EXAMPLES
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.
void
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);
}
}