xref: /freebsd/sys/kern/kern_conf.c (revision 6af83ee0d2941d18880b6aaa2b4facd1d30c6106)
1 /*-
2  * Copyright (c) 1999-2002 Poul-Henning Kamp
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/systm.h>
33 #include <sys/bio.h>
34 #include <sys/lock.h>
35 #include <sys/mutex.h>
36 #include <sys/sysctl.h>
37 #include <sys/module.h>
38 #include <sys/malloc.h>
39 #include <sys/conf.h>
40 #include <sys/vnode.h>
41 #include <sys/queue.h>
42 #include <sys/poll.h>
43 #include <sys/ctype.h>
44 #include <sys/tty.h>
45 #include <machine/stdarg.h>
46 
47 static MALLOC_DEFINE(M_DEVT, "cdev", "cdev storage");
48 
49 /* Built at compile time from sys/conf/majors */
50 extern unsigned char reserved_majors[256];
51 
52 /*
53  * This is the number of hash-buckets.  Experiments with 'real-life'
54  * dev_t's show that a prime halfway between two powers of two works
55  * best.
56  */
57 #define DEVT_HASH 83
58 
59 static LIST_HEAD(, cdev) dev_hash[DEVT_HASH];
60 
61 static struct mtx devmtx;
62 static void freedev(struct cdev *dev);
63 static struct cdev *newdev(int x, int y, struct cdev *);
64 
65 void
66 dev_lock(void)
67 {
68 	if (!mtx_initialized(&devmtx))
69 		mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
70 	mtx_lock(&devmtx);
71 }
72 
73 void
74 dev_unlock(void)
75 {
76 
77 	mtx_unlock(&devmtx);
78 }
79 
80 void
81 dev_ref(struct cdev *dev)
82 {
83 
84 	dev_lock();
85 	dev->si_refcount++;
86 	dev_unlock();
87 }
88 
89 void
90 dev_rel(struct vnode *vp)
91 {
92 	struct cdev *dev;
93 	int flag;
94 
95 	dev = vp->v_rdev;
96 	mtx_assert(&devmtx, MA_NOTOWNED);
97 	dev_lock();
98 	SLIST_REMOVE(&dev->si_hlist, vp, vnode, v_specnext);
99 	dev->si_usecount -= vp->v_usecount;
100 	vp->v_rdev = NULL;
101 	dev->si_refcount--;
102 	KASSERT(dev->si_refcount >= 0,
103 	    ("dev_rel(%s) gave negative count", devtoname(dev)));
104 	flag = 0;
105 	if (dev->si_devsw == NULL && dev->si_refcount == 0) {
106 		LIST_REMOVE(dev, si_list);
107 		flag = 1;
108 	}
109 	dev_unlock();
110 	if (flag)
111 		freedev(dev);
112 	return;
113 }
114 
115 struct cdevsw *
116 dev_refthread(struct cdev *dev)
117 {
118 	struct cdevsw *csw;
119 
120 	mtx_assert(&devmtx, MA_NOTOWNED);
121 	dev_lock();
122 	csw = dev->si_devsw;
123 	if (csw != NULL)
124 		dev->si_threadcount++;
125 	dev_unlock();
126 	return (csw);
127 }
128 
129 void
130 dev_relthread(struct cdev *dev)
131 {
132 
133 	mtx_assert(&devmtx, MA_NOTOWNED);
134 	dev_lock();
135 	dev->si_threadcount--;
136 	dev_unlock();
137 }
138 
139 int
140 nullop(void)
141 {
142 
143 	return (0);
144 }
145 
146 int
147 eopnotsupp(void)
148 {
149 
150 	return (EOPNOTSUPP);
151 }
152 
153 static int
154 enxio(void)
155 {
156 	return (ENXIO);
157 }
158 
159 static int
160 enodev(void)
161 {
162 	return (ENODEV);
163 }
164 
165 /* Define a dead_cdevsw for use when devices leave unexpectedly. */
166 
167 #define dead_open	(d_open_t *)enxio
168 #define dead_close	(d_close_t *)enxio
169 #define dead_read	(d_read_t *)enxio
170 #define dead_write	(d_write_t *)enxio
171 #define dead_ioctl	(d_ioctl_t *)enxio
172 #define dead_poll	(d_poll_t *)enodev
173 #define dead_mmap	(d_mmap_t *)enodev
174 
175 static void
176 dead_strategy(struct bio *bp)
177 {
178 
179 	biofinish(bp, NULL, ENXIO);
180 }
181 
182 #define dead_dump	(dumper_t *)enxio
183 #define dead_kqfilter	(d_kqfilter_t *)enxio
184 
185 static struct cdevsw dead_cdevsw = {
186 	.d_version =	D_VERSION,
187 	.d_flags =	D_NEEDGIANT, /* XXX: does dead_strategy need this ? */
188 	.d_open =	dead_open,
189 	.d_close =	dead_close,
190 	.d_read =	dead_read,
191 	.d_write =	dead_write,
192 	.d_ioctl =	dead_ioctl,
193 	.d_poll =	dead_poll,
194 	.d_mmap =	dead_mmap,
195 	.d_strategy =	dead_strategy,
196 	.d_name =	"dead",
197 	.d_maj =	255,
198 	.d_dump =	dead_dump,
199 	.d_kqfilter =	dead_kqfilter
200 };
201 
202 /* Default methods if driver does not specify method */
203 
204 #define null_open	(d_open_t *)nullop
205 #define null_close	(d_close_t *)nullop
206 #define no_read		(d_read_t *)enodev
207 #define no_write	(d_write_t *)enodev
208 #define no_ioctl	(d_ioctl_t *)enodev
209 #define no_mmap		(d_mmap_t *)enodev
210 #define no_kqfilter	(d_kqfilter_t *)enodev
211 
212 static void
213 no_strategy(struct bio *bp)
214 {
215 
216 	biofinish(bp, NULL, ENODEV);
217 }
218 
219 static int
220 no_poll(struct cdev *dev __unused, int events, struct thread *td __unused)
221 {
222 	/*
223 	 * Return true for read/write.  If the user asked for something
224 	 * special, return POLLNVAL, so that clients have a way of
225 	 * determining reliably whether or not the extended
226 	 * functionality is present without hard-coding knowledge
227 	 * of specific filesystem implementations.
228 	 * Stay in sync with vop_nopoll().
229 	 */
230 	if (events & ~POLLSTANDARD)
231 		return (POLLNVAL);
232 
233 	return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
234 }
235 
236 #define no_dump		(dumper_t *)enodev
237 
238 /*
239  * struct cdev * and u_dev_t primitives
240  */
241 
242 int
243 major(struct cdev *x)
244 {
245 	if (x == NULL)
246 		return NODEV;
247 	return((x->si_udev >> 8) & 0xff);
248 }
249 
250 int
251 minor(struct cdev *x)
252 {
253 	if (x == NULL)
254 		return NODEV;
255 	return(x->si_udev & MAXMINOR);
256 }
257 
258 int
259 dev2unit(struct cdev *x)
260 {
261 
262 	if (x == NULL)
263 		return NODEV;
264 	return (minor2unit(minor(x)));
265 }
266 
267 int
268 minor2unit(int _minor)
269 {
270 
271 	KASSERT((_minor & ~MAXMINOR) == 0, ("Illegal minor %x", _minor));
272 	return ((_minor & 0xff) | (_minor >> 8));
273 }
274 
275 int
276 unit2minor(int unit)
277 {
278 
279 	KASSERT(unit <= 0xffffff, ("Invalid unit (%d) in unit2minor", unit));
280 	return ((unit & 0xff) | ((unit << 8) & ~0xffff));
281 }
282 
283 static struct cdev *
284 allocdev(void)
285 {
286 	struct cdev *si;
287 
288 	si = malloc(sizeof *si, M_DEVT, M_USE_RESERVE | M_ZERO | M_WAITOK);
289 	si->si_name = si->__si_namebuf;
290 	LIST_INIT(&si->si_children);
291 	return (si);
292 }
293 
294 static struct cdev *
295 newdev(int x, int y, struct cdev *si)
296 {
297 	struct cdev *si2;
298 	dev_t	udev;
299 	int hash;
300 
301 	mtx_assert(&devmtx, MA_OWNED);
302 	if (x == umajor(NODEV) && y == uminor(NODEV))
303 		panic("newdev of NODEV");
304 	udev = (x << 8) | y;
305 	hash = udev % DEVT_HASH;
306 	LIST_FOREACH(si2, &dev_hash[hash], si_hash) {
307 		if (si2->si_udev == udev) {
308 			freedev(si);
309 			return (si2);
310 		}
311 	}
312 	si->si_udev = udev;
313 	LIST_INSERT_HEAD(&dev_hash[hash], si, si_hash);
314 	return (si);
315 }
316 
317 static void
318 freedev(struct cdev *dev)
319 {
320 
321 	free(dev, M_DEVT);
322 }
323 
324 dev_t
325 dev2udev(struct cdev *x)
326 {
327 	if (x == NULL)
328 		return (NODEV);
329 	return (x->si_udev);
330 }
331 
332 struct cdev *
333 findcdev(dev_t udev)
334 {
335 	struct cdev *si;
336 	int hash;
337 
338 	mtx_assert(&devmtx, MA_NOTOWNED);
339 	if (udev == NODEV)
340 		return (NULL);
341 	dev_lock();
342 	hash = udev % DEVT_HASH;
343 	LIST_FOREACH(si, &dev_hash[hash], si_hash) {
344 		if (si->si_udev == udev)
345 			break;
346 	}
347 	dev_unlock();
348 	return (si);
349 }
350 
351 int
352 uminor(dev_t dev)
353 {
354 	return (dev & MAXMINOR);
355 }
356 
357 int
358 umajor(dev_t dev)
359 {
360 	return ((dev & ~MAXMINOR) >> 8);
361 }
362 
363 static void
364 find_major(struct cdevsw *devsw)
365 {
366 	int i;
367 
368 	for (i = NUMCDEVSW - 1; i > 0; i--)
369 		if (reserved_majors[i] != i)
370 			break;
371 	KASSERT(i > 0, ("Out of major numbers (%s)", devsw->d_name));
372 	devsw->d_maj = i;
373 	reserved_majors[i] = i;
374 	devsw->d_flags |= D_ALLOCMAJ;
375 }
376 
377 static void
378 fini_cdevsw(struct cdevsw *devsw)
379 {
380 	if (devsw->d_flags & D_ALLOCMAJ) {
381 		reserved_majors[devsw->d_maj] = 0;
382 		devsw->d_maj = MAJOR_AUTO;
383 		devsw->d_flags &= ~D_ALLOCMAJ;
384 	} else if (devsw->d_maj == 0)
385 		devsw->d_maj = 256;
386 	devsw->d_flags &= ~D_INIT;
387 }
388 
389 static void
390 prep_cdevsw(struct cdevsw *devsw)
391 {
392 
393 	dev_lock();
394 
395 	if (devsw->d_version != D_VERSION_00) {
396 		printf(
397 		    "WARNING: Device driver \"%s\" has wrong version %s\n",
398 		    devsw->d_name, "and is disabled.  Recompile KLD module.");
399 		devsw->d_open = dead_open;
400 		devsw->d_close = dead_close;
401 		devsw->d_read = dead_read;
402 		devsw->d_write = dead_write;
403 		devsw->d_ioctl = dead_ioctl;
404 		devsw->d_poll = dead_poll;
405 		devsw->d_mmap = dead_mmap;
406 		devsw->d_strategy = dead_strategy;
407 		devsw->d_dump = dead_dump;
408 		devsw->d_kqfilter = dead_kqfilter;
409 	}
410 
411 	if (devsw->d_flags & D_TTY) {
412 		if (devsw->d_ioctl == NULL)	devsw->d_ioctl = ttyioctl;
413 		if (devsw->d_read == NULL)	devsw->d_read = ttyread;
414 		if (devsw->d_write == NULL)	devsw->d_write = ttywrite;
415 		if (devsw->d_kqfilter == NULL)	devsw->d_kqfilter = ttykqfilter;
416 		if (devsw->d_poll == NULL)	devsw->d_poll = ttypoll;
417 	}
418 
419 	if (devsw->d_open == NULL)	devsw->d_open = null_open;
420 	if (devsw->d_close == NULL)	devsw->d_close = null_close;
421 	if (devsw->d_read == NULL)	devsw->d_read = no_read;
422 	if (devsw->d_write == NULL)	devsw->d_write = no_write;
423 	if (devsw->d_ioctl == NULL)	devsw->d_ioctl = no_ioctl;
424 	if (devsw->d_poll == NULL)	devsw->d_poll = no_poll;
425 	if (devsw->d_mmap == NULL)	devsw->d_mmap = no_mmap;
426 	if (devsw->d_strategy == NULL)	devsw->d_strategy = no_strategy;
427 	if (devsw->d_dump == NULL)	devsw->d_dump = no_dump;
428 	if (devsw->d_kqfilter == NULL)	devsw->d_kqfilter = no_kqfilter;
429 
430 	LIST_INIT(&devsw->d_devs);
431 
432 	devsw->d_flags |= D_INIT;
433 
434 	if (devsw->d_maj == MAJOR_AUTO) {
435 		find_major(devsw);
436 	} else {
437 		if (devsw->d_maj == 256)	/* XXX: tty_cons.c is magic */
438 			devsw->d_maj = 0;
439 		KASSERT(devsw->d_maj >= 0 && devsw->d_maj < 256,
440 		    ("Invalid major (%d) in make_dev", devsw->d_maj));
441 		if (reserved_majors[devsw->d_maj] != devsw->d_maj) {
442 			printf("WARNING: driver \"%s\" used %s %d\n",
443 			    devsw->d_name, "unreserved major device number",
444 			    devsw->d_maj);
445 			reserved_majors[devsw->d_maj] = devsw->d_maj;
446 		}
447 	}
448 	dev_unlock();
449 }
450 
451 struct cdev *
452 make_dev(struct cdevsw *devsw, int minornr, uid_t uid, gid_t gid, int perms, const char *fmt, ...)
453 {
454 	struct cdev *dev;
455 	va_list ap;
456 	int i;
457 
458 	KASSERT((minornr & ~MAXMINOR) == 0,
459 	    ("Invalid minor (0x%x) in make_dev", minornr));
460 
461 	if (!(devsw->d_flags & D_INIT))
462 		prep_cdevsw(devsw);
463 	dev = allocdev();
464 	dev_lock();
465 	dev = newdev(devsw->d_maj, minornr, dev);
466 	if (dev->si_flags & SI_CHEAPCLONE &&
467 	    dev->si_flags & SI_NAMED &&
468 	    dev->si_devsw == devsw) {
469 		/*
470 		 * This is allowed as it removes races and generally
471 		 * simplifies cloning devices.
472 		 * XXX: still ??
473 		 */
474 		dev_unlock();
475 		return (dev);
476 	}
477 	KASSERT(!(dev->si_flags & SI_NAMED),
478 	    ("make_dev() by driver %s on pre-existing device (maj=%d, min=%d, name=%s)",
479 	    devsw->d_name, major(dev), minor(dev), devtoname(dev)));
480 
481 	va_start(ap, fmt);
482 	i = vsnrprintf(dev->__si_namebuf, sizeof dev->__si_namebuf, 32, fmt, ap);
483 	if (i > (sizeof dev->__si_namebuf - 1)) {
484 		printf("WARNING: Device name truncated! (%s)\n",
485 		    dev->__si_namebuf);
486 	}
487 	va_end(ap);
488 
489 	dev->si_devsw = devsw;
490 	dev->si_uid = uid;
491 	dev->si_gid = gid;
492 	dev->si_mode = perms;
493 	dev->si_flags |= SI_NAMED;
494 
495 	LIST_INSERT_HEAD(&devsw->d_devs, dev, si_list);
496 	devfs_create(dev);
497 	dev_unlock();
498 	return (dev);
499 }
500 
501 int
502 dev_named(struct cdev *pdev, const char *name)
503 {
504 	struct cdev *cdev;
505 
506 	if (strcmp(devtoname(pdev), name) == 0)
507 		return (1);
508 	LIST_FOREACH(cdev, &pdev->si_children, si_siblings)
509 		if (strcmp(devtoname(cdev), name) == 0)
510 			return (1);
511 	return (0);
512 }
513 
514 void
515 dev_depends(struct cdev *pdev, struct cdev *cdev)
516 {
517 
518 	dev_lock();
519 	cdev->si_parent = pdev;
520 	cdev->si_flags |= SI_CHILD;
521 	LIST_INSERT_HEAD(&pdev->si_children, cdev, si_siblings);
522 	dev_unlock();
523 }
524 
525 struct cdev *
526 make_dev_alias(struct cdev *pdev, const char *fmt, ...)
527 {
528 	struct cdev *dev;
529 	va_list ap;
530 	int i;
531 
532 	dev = allocdev();
533 	dev_lock();
534 	dev->si_flags |= SI_ALIAS;
535 	dev->si_flags |= SI_NAMED;
536 	va_start(ap, fmt);
537 	i = vsnrprintf(dev->__si_namebuf, sizeof dev->__si_namebuf, 32, fmt, ap);
538 	if (i > (sizeof dev->__si_namebuf - 1)) {
539 		printf("WARNING: Device name truncated! (%s)\n",
540 		    dev->__si_namebuf);
541 	}
542 	va_end(ap);
543 
544 	devfs_create(dev);
545 	dev_unlock();
546 	dev_depends(pdev, dev);
547 	return (dev);
548 }
549 
550 static void
551 idestroy_dev(struct cdev *dev)
552 {
553 	struct cdevsw *csw;
554 
555 	KASSERT(dev->si_flags & SI_NAMED,
556 	    ("WARNING: Driver mistake: destroy_dev on %d/%d\n",
557 	    major(dev), minor(dev)));
558 
559 	devfs_destroy(dev);
560 
561 	/* Remove name marking */
562 	dev->si_flags &= ~SI_NAMED;
563 
564 	/* If we are a child, remove us from the parents list */
565 	if (dev->si_flags & SI_CHILD) {
566 		LIST_REMOVE(dev, si_siblings);
567 		dev->si_flags &= ~SI_CHILD;
568 	}
569 
570 	/* Kill our children */
571 	while (!LIST_EMPTY(&dev->si_children))
572 		idestroy_dev(LIST_FIRST(&dev->si_children));
573 
574 	/* Remove from clone list */
575 	if (dev->si_flags & SI_CLONELIST) {
576 		LIST_REMOVE(dev, si_clone);
577 		dev->si_flags &= ~SI_CLONELIST;
578 	}
579 
580 	csw = dev->si_devsw;
581 	dev->si_devsw = NULL;	/* already NULL for SI_ALIAS */
582 	while (csw != NULL && csw->d_purge != NULL && dev->si_threadcount) {
583 		printf("Purging %lu threads from %s\n",
584 		    dev->si_threadcount, devtoname(dev));
585 		csw->d_purge(dev);
586 		msleep(csw, &devmtx, PRIBIO, "devprg", hz/10);
587 	}
588 	if (csw != NULL && csw->d_purge != NULL)
589 		printf("All threads purged from %s\n", devtoname(dev));
590 
591 	dev->si_drv1 = 0;
592 	dev->si_drv2 = 0;
593 	bzero(&dev->__si_u, sizeof(dev->__si_u));
594 
595 	if (!(dev->si_flags & SI_ALIAS)) {
596 		/* Remove from cdevsw list */
597 		LIST_REMOVE(dev, si_list);
598 
599 		/* If cdevsw has no struct cdev *'s, clean it */
600 		if (LIST_EMPTY(&csw->d_devs))
601 			fini_cdevsw(csw);
602 
603 		LIST_REMOVE(dev, si_hash);
604 	}
605 	dev->si_flags &= ~SI_ALIAS;
606 
607 	if (dev->si_refcount > 0) {
608 		LIST_INSERT_HEAD(&dead_cdevsw.d_devs, dev, si_list);
609 	} else {
610 		freedev(dev);
611 	}
612 }
613 
614 void
615 destroy_dev(struct cdev *dev)
616 {
617 
618 	dev_lock();
619 	idestroy_dev(dev);
620 	dev_unlock();
621 }
622 
623 const char *
624 devtoname(struct cdev *dev)
625 {
626 	char *p;
627 	struct cdevsw *csw;
628 	int mynor;
629 
630 	if (dev->si_name[0] == '#' || dev->si_name[0] == '\0') {
631 		p = dev->si_name;
632 		sprintf(p, "#%d", major(dev));
633 		p += strlen(p);
634 		csw = dev_refthread(dev);
635 		if (csw != NULL) {
636 			sprintf(p, "(%s)", csw->d_name);
637 			dev_relthread(dev);
638 		}
639 		p += strlen(p);
640 		mynor = minor(dev);
641 		if (mynor < 0 || mynor > 255)
642 			sprintf(p, "/%#x", (u_int)mynor);
643 		else
644 			sprintf(p, "/%d", mynor);
645 	}
646 	return (dev->si_name);
647 }
648 
649 int
650 dev_stdclone(char *name, char **namep, const char *stem, int *unit)
651 {
652 	int u, i;
653 
654 	i = strlen(stem);
655 	if (bcmp(stem, name, i) != 0)
656 		return (0);
657 	if (!isdigit(name[i]))
658 		return (0);
659 	u = 0;
660 	if (name[i] == '0' && isdigit(name[i+1]))
661 		return (0);
662 	while (isdigit(name[i])) {
663 		u *= 10;
664 		u += name[i++] - '0';
665 	}
666 	if (u > 0xffffff)
667 		return (0);
668 	*unit = u;
669 	if (namep)
670 		*namep = &name[i];
671 	if (name[i])
672 		return (2);
673 	return (1);
674 }
675 
676 /*
677  * Helper functions for cloning device drivers.
678  *
679  * The objective here is to make it unnecessary for the device drivers to
680  * use rman or similar to manage their unit number space.  Due to the way
681  * we do "on-demand" devices, using rman or other "private" methods
682  * will be very tricky to lock down properly once we lock down this file.
683  *
684  * Instead we give the drivers these routines which puts the struct cdev *'s
685  * that are to be managed on their own list, and gives the driver the ability
686  * to ask for the first free unit number or a given specified unit number.
687  *
688  * In addition these routines support paired devices (pty, nmdm and similar)
689  * by respecting a number of "flag" bits in the minor number.
690  *
691  */
692 
693 struct clonedevs {
694 	LIST_HEAD(,cdev)	head;
695 };
696 
697 void
698 clone_setup(struct clonedevs **cdp)
699 {
700 
701 	*cdp = malloc(sizeof **cdp, M_DEVBUF, M_WAITOK | M_ZERO);
702 	LIST_INIT(&(*cdp)->head);
703 }
704 
705 int
706 clone_create(struct clonedevs **cdp, struct cdevsw *csw, int *up, struct cdev **dp, u_int extra)
707 {
708 	struct clonedevs *cd;
709 	struct cdev *dev, *ndev, *dl, *de;
710 	int unit, low, u;
711 
712 	KASSERT(*cdp != NULL,
713 	    ("clone_setup() not called in driver \"%s\"", csw->d_name));
714 	KASSERT(!(extra & CLONE_UNITMASK),
715 	    ("Illegal extra bits (0x%x) in clone_create", extra));
716 	KASSERT(*up <= CLONE_UNITMASK,
717 	    ("Too high unit (0x%x) in clone_create", *up));
718 
719 	if (csw->d_maj == MAJOR_AUTO)
720 		find_major(csw);
721 
722 	/*
723 	 * Search the list for a lot of things in one go:
724 	 *   A preexisting match is returned immediately.
725 	 *   The lowest free unit number if we are passed -1, and the place
726 	 *	 in the list where we should insert that new element.
727 	 *   The place to insert a specified unit number, if applicable
728 	 *       the end of the list.
729 	 */
730 	unit = *up;
731 	ndev = allocdev();
732 	dev_lock();
733 	low = extra;
734 	de = dl = NULL;
735 	cd = *cdp;
736 	LIST_FOREACH(dev, &cd->head, si_clone) {
737 		KASSERT(dev->si_flags & SI_CLONELIST,
738 		    ("Dev %p(%s) should be on clonelist", dev, dev->si_name));
739 		u = dev2unit(dev);
740 		if (u == (unit | extra)) {
741 			*dp = dev;
742 			freedev(ndev);
743 			dev_unlock();
744 			return (0);
745 		}
746 		if (unit == -1 && u == low) {
747 			low++;
748 			de = dev;
749 			continue;
750 		}
751 		if (u > (unit | extra)) {
752 			dl = dev;
753 			break;
754 		}
755 	}
756 	if (unit == -1)
757 		unit = low & CLONE_UNITMASK;
758 	dev = newdev(csw->d_maj, unit2minor(unit | extra), ndev);
759 	if (dev->si_flags & SI_CLONELIST) {
760 		printf("dev %p (%s) is on clonelist\n", dev, dev->si_name);
761 		printf("unit=%d\n", unit);
762 		LIST_FOREACH(dev, &cd->head, si_clone) {
763 			printf("\t%p %s\n", dev, dev->si_name);
764 		}
765 		panic("foo");
766 	}
767 	KASSERT(!(dev->si_flags & SI_CLONELIST),
768 	    ("Dev %p(%s) should not be on clonelist", dev, dev->si_name));
769 	if (dl != NULL)
770 		LIST_INSERT_BEFORE(dl, dev, si_clone);
771 	else if (de != NULL)
772 		LIST_INSERT_AFTER(de, dev, si_clone);
773 	else
774 		LIST_INSERT_HEAD(&cd->head, dev, si_clone);
775 	dev->si_flags |= SI_CLONELIST;
776 	*up = unit;
777 	dev_unlock();
778 	return (1);
779 }
780 
781 /*
782  * Kill everything still on the list.  The driver should already have
783  * disposed of any softc hung of the struct cdev *'s at this time.
784  */
785 void
786 clone_cleanup(struct clonedevs **cdp)
787 {
788 	struct cdev *dev, *tdev;
789 	struct clonedevs *cd;
790 
791 	cd = *cdp;
792 	if (cd == NULL)
793 		return;
794 	dev_lock();
795 	LIST_FOREACH_SAFE(dev, &cd->head, si_clone, tdev) {
796 		KASSERT(dev->si_flags & SI_CLONELIST,
797 		    ("Dev %p(%s) should be on clonelist", dev, dev->si_name));
798 		KASSERT(dev->si_flags & SI_NAMED,
799 		    ("Driver has goofed in cloning underways udev %x", dev->si_udev));
800 		idestroy_dev(dev);
801 	}
802 	dev_unlock();
803 	free(cd, M_DEVBUF);
804 	*cdp = NULL;
805 }
806 
807 /*
808  * Helper sysctl for devname(3).  We're given a struct cdev * and return
809  * the name, if any, registered by the device driver.
810  */
811 static int
812 sysctl_devname(SYSCTL_HANDLER_ARGS)
813 {
814 	int error;
815 	dev_t ud;
816 	struct cdev *dev;
817 
818 	error = SYSCTL_IN(req, &ud, sizeof (ud));
819 	if (error)
820 		return (error);
821 	if (ud == NODEV)
822 		return(EINVAL);
823 	dev = findcdev(ud);
824 	if (dev == NULL)
825 		error = ENOENT;
826 	else
827 		error = SYSCTL_OUT(req, dev->si_name, strlen(dev->si_name) + 1);
828 	return (error);
829 }
830 
831 SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_ANYBODY,
832 	NULL, 0, sysctl_devname, "", "devname(3) handler");
833