Function clone_create

freebsd/kern/kern_conf.c:1308–1389

}

int
clone_create(struct clonedevs **cdp, struct cdevsw *csw, int *up,
    struct cdev **dp, int extra)
{
	struct clonedevs *cd;
	struct cdev *dev, *ndev, *dl, *de;
	struct make_dev_args args;
	int unit, low, u;

	KASSERT(*cdp != NULL,
	    ("clone_setup() not called in driver \"%s\"", csw->d_name));
	KASSERT(!(extra & CLONE_UNITMASK),
	    ("Illegal extra bits (0x%x) in clone_create", extra));
	KASSERT(*up <= CLONE_UNITMASK,
	    ("Too high unit (0x%x) in clone_create", *up));
	KASSERT(csw->d_flags & D_NEEDMINOR,
	    ("clone_create() on cdevsw without minor numbers"));

	/*
	 * Search the list for a lot of things in one go:
	 *   A preexisting match is returned immediately.
	 *   The lowest free unit number if we are passed -1, and the place
	 *	 in the list where we should insert that new element.
	 *   The place to insert a specified unit number, if applicable
	 *       the end of the list.
	 */
	unit = *up;
	ndev = devfs_alloc(MAKEDEV_WAITOK);
	dev_lock();
	prep_cdevsw(csw, MAKEDEV_WAITOK);
	low = extra;
	de = dl = NULL;
	cd = *cdp;
	LIST_FOREACH(dev, &cd->head, si_clone) {
		KASSERT(dev->si_flags & SI_CLONELIST,
		    ("Dev %p(%s) should be on clonelist", dev, dev->si_name));
		u = dev2unit(dev);
		if (u == (unit | extra)) {
			*dp = dev;
			dev_unlock();
			devfs_free(ndev);
			return (0);
		}
		if (unit == -1 && u == low) {
			low++;
			de = dev;
			continue;
		} else if (u < (unit | extra)) {
			de = dev;
			continue;
		} else if (u > (unit | extra)) {
			dl = dev;
			break;
		}
	}
	if (unit == -1)
		unit = low & CLONE_UNITMASK;
	make_dev_args_init(&args);