Basic Examples

Before any communication can occur with a device, it needs to be found. This is accomplished by finding all of the busses and then finding all of the devices on all of the busses:

	struct usb_bus *busses;

	usb_init();
	usb_find_busses();
	usb_find_devices();

	busses = usb_get_busses();
    

After this, the application should manually loop through all of the busess and all of the devices and matching the device by whatever criteria is needed:

	struct usb_bus *bus;
	int c, i, a;

	/* ... */

	for (bus = busses; bus; bus = bus->next) {
		struct usb_device *dev;

		for (dev = bus->devices; dev; dev = dev->next) {
			/* Check if this device is a printer */
			if (dev->descriptor.bDeviceClass == 7) {
				/* Open the device, claim the interface and do your processing */
				...
			}

			/* Loop through all of the configurations */
			for (c = 0; c < dev->descriptor.bNumConfigurations; c++) {
				/* Loop through all of the interfaces */
				for (i = 0; i < dev->config[c].bNumInterfaces; i++) {
					/* Loop through all of the alternate settings */
					for (a = 0; a < dev->config[c].interface[i].num_altsetting; a++) {
						/* Check if this interface is a printer */
						if (dev->config[c].interface[i].altsetting[a].bInterfaceClass == 7) {
							/* Open the device, set the alternate setting, claim the interface and do your processing */
							...
						}
					}
				}
			}
		}
	}