xref: /dragonfly/sys/kern/subr_rman.c (revision a3127495)
1 /*
2  * Copyright 1998 Massachusetts Institute of Technology
3  *
4  * Permission to use, copy, modify, and distribute this software and
5  * its documentation for any purpose and without fee is hereby
6  * granted, provided that both the above copyright notice and this
7  * permission notice appear in all copies, that both the above
8  * copyright notice and this permission notice appear in all
9  * supporting documentation, and that the name of M.I.T. not be used
10  * in advertising or publicity pertaining to distribution of the
11  * software without specific, written prior permission.  M.I.T. makes
12  * no representations about the suitability of this software for any
13  * purpose.  It is provided "as is" without express or implied
14  * warranty.
15  *
16  * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
17  * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
18  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
20  * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
23  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
25  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
26  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * $FreeBSD: src/sys/kern/subr_rman.c,v 1.10.2.1 2001/06/05 08:06:08 imp Exp $
30  */
31 
32 /*
33  * The kernel resource manager.  This code is responsible for keeping track
34  * of hardware resources which are apportioned out to various drivers.
35  * It does not actually assign those resources, and it is not expected
36  * that end-device drivers will call into this code directly.  Rather,
37  * the code which implements the buses that those devices are attached to,
38  * and the code which manages CPU resources, will call this code, and the
39  * end-device drivers will make upcalls to that code to actually perform
40  * the allocation.
41  *
42  * There are two sorts of resources managed by this code.  The first is
43  * the more familiar array (RMAN_ARRAY) type; resources in this class
44  * consist of a sequence of individually-allocatable objects which have
45  * been numbered in some well-defined order.  Most of the resources
46  * are of this type, as it is the most familiar.  The second type is
47  * called a gauge (RMAN_GAUGE), and models fungible resources (i.e.,
48  * resources in which each instance is indistinguishable from every
49  * other instance).  The principal anticipated application of gauges
50  * is in the context of power consumption, where a bus may have a specific
51  * power budget which all attached devices share.  RMAN_GAUGE is not
52  * implemented yet.
53  *
54  * For array resources, we make one simplifying assumption: two clients
55  * sharing the same resource must use the same range of indices.  That
56  * is to say, sharing of overlapping-but-not-identical regions is not
57  * permitted.
58  */
59 
60 #include <sys/param.h>
61 #include <sys/systm.h>
62 #include <sys/kernel.h>
63 #include <sys/lock.h>
64 #include <sys/malloc.h>
65 #include <sys/bus.h>		/* XXX debugging */
66 #include <sys/rman.h>
67 #include <sys/sysctl.h>
68 
69 int	rman_debug = 0;
70 TUNABLE_INT("debug.rman_debug", &rman_debug);
71 SYSCTL_INT(_debug, OID_AUTO, rman_debug, CTLFLAG_RW,
72     &rman_debug, 0, "rman debug");
73 
74 #define DPRINTF(params) if (rman_debug) kprintf params
75 
76 static MALLOC_DEFINE(M_RMAN, "rman", "Resource manager");
77 
78 struct	rman_head rman_head;
79 static	struct lwkt_token rman_tok; /* mutex to protect rman_head */
80 static	int int_rman_activate_resource(struct rman *rm, struct resource *r,
81 				       struct resource **whohas);
82 static	int int_rman_deactivate_resource(struct resource *r);
83 static	int int_rman_release_resource(struct rman *rm, struct resource *r);
84 
85 int
86 rman_init(struct rman *rm, int cpuid)
87 {
88 	static int once;
89 
90 	if (once == 0) {
91 		once = 1;
92 		TAILQ_INIT(&rman_head);
93 		lwkt_token_init(&rman_tok, "rman");
94 	}
95 
96 	if (rm->rm_type == RMAN_UNINIT)
97 		panic("rman_init");
98 	if (rm->rm_type == RMAN_GAUGE)
99 		panic("implement RMAN_GAUGE");
100 
101 	TAILQ_INIT(&rm->rm_list);
102 	rm->rm_slock = kmalloc(sizeof *rm->rm_slock, M_RMAN, M_NOWAIT);
103 	if (rm->rm_slock == NULL)
104 		return ENOMEM;
105 	lwkt_token_init(rm->rm_slock, "rmanslock");
106 
107 	rm->rm_cpuid = cpuid;
108 
109 	lwkt_gettoken(&rman_tok);
110 	TAILQ_INSERT_TAIL(&rman_head, rm, rm_link);
111 	lwkt_reltoken(&rman_tok);
112 	return 0;
113 }
114 
115 /*
116  * NB: this interface is not robust against programming errors which
117  * add multiple copies of the same region.
118  */
119 int
120 rman_manage_region(struct rman *rm, u_long start, u_long end)
121 {
122 	struct resource *r, *s;
123 
124 	DPRINTF(("rman_manage_region: <%s> request: start %#lx, end %#lx\n",
125 	    rm->rm_descr, start, end));
126 	r = kmalloc(sizeof *r, M_RMAN, M_NOWAIT | M_ZERO);
127 	if (r == NULL)
128 		return ENOMEM;
129 	r->r_sharehead = 0;
130 	r->r_start = start;
131 	r->r_end = end;
132 	r->r_flags = 0;
133 	r->r_dev = 0;
134 	r->r_rm = rm;
135 
136 	lwkt_gettoken(rm->rm_slock);
137 	for (s = TAILQ_FIRST(&rm->rm_list);
138 	     s && s->r_end < r->r_start;
139 	     s = TAILQ_NEXT(s, r_link))
140 		;
141 
142 	if (s == NULL)
143 		TAILQ_INSERT_TAIL(&rm->rm_list, r, r_link);
144 	else
145 		TAILQ_INSERT_BEFORE(s, r, r_link);
146 
147 	lwkt_reltoken(rm->rm_slock);
148 	return 0;
149 }
150 
151 int
152 rman_fini(struct rman *rm)
153 {
154 	struct resource *r;
155 
156 	lwkt_gettoken(rm->rm_slock);
157 	TAILQ_FOREACH(r, &rm->rm_list, r_link) {
158 		if (r->r_flags & RF_ALLOCATED) {
159 			lwkt_reltoken(rm->rm_slock);
160 			return EBUSY;
161 		}
162 	}
163 
164 	/*
165 	 * There really should only be one of these if we are in this
166 	 * state and the code is working properly, but it can't hurt.
167 	 */
168 	while (!TAILQ_EMPTY(&rm->rm_list)) {
169 		r = TAILQ_FIRST(&rm->rm_list);
170 		TAILQ_REMOVE(&rm->rm_list, r, r_link);
171 		kfree(r, M_RMAN);
172 	}
173 	lwkt_reltoken(rm->rm_slock);
174 
175 	/* XXX what's the point of this if we are going to free the struct? */
176 	lwkt_gettoken(&rman_tok);
177 	TAILQ_REMOVE(&rman_head, rm, rm_link);
178 	lwkt_reltoken(&rman_tok);
179 	kfree(rm->rm_slock, M_RMAN);
180 
181 	return 0;
182 }
183 
184 struct resource *
185 rman_reserve_resource(struct rman *rm, u_long start, u_long end, u_long count,
186 		      u_int flags, device_t dev)
187 {
188 	u_int	want_activate;
189 	struct	resource *r, *s, *rv;
190 	u_long	rstart, rend;
191 
192 	rv = NULL;
193 
194 	DPRINTF(("rman_reserve_resource: <%s> request: [%#lx, %#lx], length "
195 	       "%#lx, flags %u, device %s\n", rm->rm_descr, start, end,
196 	       count, flags,
197 	       dev == NULL ? "<null>" : device_get_nameunit(dev)));
198 	want_activate = (flags & RF_ACTIVE);
199 	flags &= ~RF_ACTIVE;
200 
201 	lwkt_gettoken(rm->rm_slock);
202 
203 	for (r = TAILQ_FIRST(&rm->rm_list);
204 	     r && r->r_end < start + count - 1;
205 	     r = TAILQ_NEXT(r, r_link))
206 		;
207 
208 	if (r == NULL) {
209 		DPRINTF(("could not find a region\n"));
210 		goto out;
211 	}
212 
213 	/*
214 	 * First try to find an acceptable totally-unshared region.
215 	 */
216 	for (s = r; s; s = TAILQ_NEXT(s, r_link)) {
217 		DPRINTF(("considering [%#lx, %#lx]\n", s->r_start, s->r_end));
218 		if (s->r_start > end - (count - 1)) {
219 			DPRINTF(("s->r_start (%#lx) > end (%#lx)\n",
220 			    s->r_start, end));
221 			break;
222 		}
223 		if (s->r_flags & RF_ALLOCATED) {
224 			DPRINTF(("region is allocated\n"));
225 			continue;
226 		}
227 		rstart = ulmax(s->r_start, start);
228 		rstart = (rstart + ((1ul << RF_ALIGNMENT(flags))) - 1) &
229 		    ~((1ul << RF_ALIGNMENT(flags)) - 1);
230 		rend = ulmin(s->r_end, ulmax(start + count - 1, end));
231 		DPRINTF(("truncated region: [%#lx, %#lx]; size %#lx (requested %#lx)\n",
232 		       rstart, rend, (rend - rstart + 1), count));
233 
234 		if ((rend - rstart + 1) >= count) {
235 			DPRINTF(("candidate region: [%#lx, %#lx], size %#lx\n",
236 			       rstart, rend, (rend - rstart + 1)));
237 			if ((s->r_end - s->r_start + 1) == count) {
238 				DPRINTF(("candidate region is entire chunk\n"));
239 				rv = s;
240 				rv->r_flags |= RF_ALLOCATED | flags;
241 				rv->r_dev = dev;
242 				goto out;
243 			}
244 
245 			/*
246 			 * If s->r_start < rstart and
247 			 *    s->r_end > rstart + count - 1, then
248 			 * we need to split the region into three pieces
249 			 * (the middle one will get returned to the user).
250 			 * Otherwise, we are allocating at either the
251 			 * beginning or the end of s, so we only need to
252 			 * split it in two.  The first case requires
253 			 * two new allocations; the second requires but one.
254 			 */
255 			rv = kmalloc(sizeof *rv, M_RMAN, M_NOWAIT | M_ZERO);
256 			if (rv == NULL)
257 				goto out;
258 			rv->r_start = rstart;
259 			rv->r_end = rstart + count - 1;
260 			rv->r_flags = flags | RF_ALLOCATED;
261 			rv->r_dev = dev;
262 			rv->r_sharehead = 0;
263 			rv->r_rm = rm;
264 
265 			if (s->r_start < rv->r_start && s->r_end > rv->r_end) {
266 				DPRINTF(("splitting region in three parts: "
267 				       "[%#lx, %#lx]; [%#lx, %#lx]; [%#lx, %#lx]\n",
268 				       s->r_start, rv->r_start - 1,
269 				       rv->r_start, rv->r_end,
270 				       rv->r_end + 1, s->r_end));
271 				/*
272 				 * We are allocating in the middle.
273 				 */
274 				r = kmalloc(sizeof *r, M_RMAN,
275 				    M_NOWAIT | M_ZERO);
276 				if (r == NULL) {
277 					kfree(rv, M_RMAN);
278 					rv = NULL;
279 					goto out;
280 				}
281 				r->r_start = rv->r_end + 1;
282 				r->r_end = s->r_end;
283 				r->r_flags = s->r_flags;
284 				r->r_dev = 0;
285 				r->r_sharehead = 0;
286 				r->r_rm = rm;
287 				s->r_end = rv->r_start - 1;
288 				TAILQ_INSERT_AFTER(&rm->rm_list, s, rv,
289 						     r_link);
290 				TAILQ_INSERT_AFTER(&rm->rm_list, rv, r,
291 						     r_link);
292 			} else if (s->r_start == rv->r_start) {
293 				DPRINTF(("allocating from the beginning\n"));
294 				/*
295 				 * We are allocating at the beginning.
296 				 */
297 				s->r_start = rv->r_end + 1;
298 				TAILQ_INSERT_BEFORE(s, rv, r_link);
299 			} else {
300 				DPRINTF(("allocating at the end\n"));
301 				/*
302 				 * We are allocating at the end.
303 				 */
304 				s->r_end = rv->r_start - 1;
305 				TAILQ_INSERT_AFTER(&rm->rm_list, s, rv,
306 						     r_link);
307 			}
308 			goto out;
309 		}
310 	}
311 
312 	/*
313 	 * Now find an acceptable shared region, if the client's requirements
314 	 * allow sharing.  By our implementation restriction, a candidate
315 	 * region must match exactly by both size and sharing type in order
316 	 * to be considered compatible with the client's request.  (The
317 	 * former restriction could probably be lifted without too much
318 	 * additional work, but this does not seem warranted.)
319 	 */
320 	DPRINTF(("no unshared regions found\n"));
321 	if ((flags & (RF_SHAREABLE | RF_TIMESHARE)) == 0)
322 		goto out;
323 
324 	for (s = r; s; s = TAILQ_NEXT(s, r_link)) {
325 		if (s->r_start > end)
326 			break;
327 		if ((s->r_flags & flags) != flags)
328 			continue;
329 		rstart = ulmax(s->r_start, start);
330 		rend = ulmin(s->r_end, ulmax(start + count, end));
331 		if (s->r_start >= start && s->r_end <= end
332 		    && (s->r_end - s->r_start + 1) == count) {
333 			rv = kmalloc(sizeof *rv, M_RMAN, M_NOWAIT | M_ZERO);
334 			if (rv == NULL)
335 				goto out;
336 			rv->r_start = s->r_start;
337 			rv->r_end = s->r_end;
338 			rv->r_flags = s->r_flags &
339 				(RF_ALLOCATED | RF_SHAREABLE | RF_TIMESHARE);
340 			rv->r_dev = dev;
341 			rv->r_rm = rm;
342 			if (s->r_sharehead == 0) {
343 				s->r_sharehead = kmalloc(sizeof *s->r_sharehead,
344 							M_RMAN,
345 							M_NOWAIT | M_ZERO);
346 				if (s->r_sharehead == 0) {
347 					kfree(rv, M_RMAN);
348 					rv = NULL;
349 					goto out;
350 				}
351 				LIST_INIT(s->r_sharehead);
352 				LIST_INSERT_HEAD(s->r_sharehead, s,
353 						 r_sharelink);
354 				s->r_flags |= RF_FIRSTSHARE;
355 			}
356 			rv->r_sharehead = s->r_sharehead;
357 			LIST_INSERT_HEAD(s->r_sharehead, rv, r_sharelink);
358 			goto out;
359 		}
360 	}
361 
362 	/*
363 	 * We couldn't find anything.
364 	 */
365 	DPRINTF(("no region found\n"));
366 out:
367 	/*
368 	 * If the user specified RF_ACTIVE in the initial flags,
369 	 * which is reflected in `want_activate', we attempt to atomically
370 	 * activate the resource.  If this fails, we release the resource
371 	 * and indicate overall failure.  (This behavior probably doesn't
372 	 * make sense for RF_TIMESHARE-type resources.)
373 	 */
374 	if (rv && want_activate) {
375 		struct resource *whohas;
376 		DPRINTF(("activating region\n"));
377 		if (int_rman_activate_resource(rm, rv, &whohas)) {
378 			int_rman_release_resource(rm, rv);
379 			rv = NULL;
380 		}
381 	}
382 	lwkt_reltoken(rm->rm_slock);
383 	return (rv);
384 }
385 
386 static int
387 int_rman_activate_resource(struct rman *rm, struct resource *r,
388 			   struct resource **whohas)
389 {
390 	struct resource *s;
391 	int ok;
392 
393 	/*
394 	 * If we are not timesharing, then there is nothing much to do.
395 	 * If we already have the resource, then there is nothing at all to do.
396 	 * If we are not on a sharing list with anybody else, then there is
397 	 * little to do.
398 	 */
399 	if ((r->r_flags & RF_TIMESHARE) == 0
400 	    || (r->r_flags & RF_ACTIVE) != 0
401 	    || r->r_sharehead == 0) {
402 		r->r_flags |= RF_ACTIVE;
403 		return 0;
404 	}
405 
406 	ok = 1;
407 	for (s = LIST_FIRST(r->r_sharehead); s && ok;
408 	     s = LIST_NEXT(s, r_sharelink)) {
409 		if ((s->r_flags & RF_ACTIVE) != 0) {
410 			ok = 0;
411 			*whohas = s;
412 		}
413 	}
414 	if (ok) {
415 		r->r_flags |= RF_ACTIVE;
416 		return 0;
417 	}
418 	return EBUSY;
419 }
420 
421 int
422 rman_activate_resource(struct resource *r)
423 {
424 	int rv;
425 	struct resource *whohas;
426 	struct rman *rm;
427 
428 	rm = r->r_rm;
429 	lwkt_gettoken(rm->rm_slock);
430 	rv = int_rman_activate_resource(rm, r, &whohas);
431 	lwkt_reltoken(rm->rm_slock);
432 	return rv;
433 }
434 
435 #if 0
436 
437 /* XXX */
438 int
439 rman_await_resource(struct resource *r, int slpflags, int timo)
440 {
441 	int	rv;
442 	struct	resource *whohas;
443 	struct	rman *rm;
444 
445 	rm = r->r_rm;
446 	for (;;) {
447 		lwkt_gettoken(rm->rm_slock);
448 		rv = int_rman_activate_resource(rm, r, &whohas);
449 		if (rv != EBUSY)
450 			return (rv);	/* returns with ilock held */
451 
452 		if (r->r_sharehead == 0)
453 			panic("rman_await_resource");
454 		/*
455 		 * A critical section will hopefully will prevent a race
456 		 * between lwkt_reltoken and tsleep where a process
457 		 * could conceivably get in and release the resource
458 		 * before we have a chance to sleep on it. YYY
459 		 */
460 		crit_enter();
461 		whohas->r_flags |= RF_WANTED;
462 		rv = tsleep(r->r_sharehead, slpflags, "rmwait", timo);
463 		if (rv) {
464 			lwkt_reltoken(rm->rm_slock);
465 			crit_exit();
466 			return rv;
467 		}
468 		crit_exit();
469 	}
470 }
471 
472 #endif
473 
474 static int
475 int_rman_deactivate_resource(struct resource *r)
476 {
477 	r->r_flags &= ~RF_ACTIVE;
478 	if (r->r_flags & RF_WANTED) {
479 		r->r_flags &= ~RF_WANTED;
480 		wakeup(r->r_sharehead);
481 	}
482 	return 0;
483 }
484 
485 int
486 rman_deactivate_resource(struct resource *r)
487 {
488 	struct rman *rm;
489 
490 	rm = r->r_rm;
491 	lwkt_gettoken(rm->rm_slock);
492 	int_rman_deactivate_resource(r);
493 	lwkt_reltoken(rm->rm_slock);
494 	return 0;
495 }
496 
497 static int
498 int_rman_release_resource(struct rman *rm, struct resource *r)
499 {
500 	struct	resource *s, *t;
501 
502 	if (r->r_flags & RF_ACTIVE)
503 		int_rman_deactivate_resource(r);
504 
505 	/*
506 	 * Check for a sharing list first.  If there is one, then we don't
507 	 * have to think as hard.
508 	 */
509 	if (r->r_sharehead) {
510 		/*
511 		 * If a sharing list exists, then we know there are at
512 		 * least two sharers.
513 		 *
514 		 * If we are in the main circleq, appoint someone else.
515 		 */
516 		LIST_REMOVE(r, r_sharelink);
517 		s = LIST_FIRST(r->r_sharehead);
518 		if (r->r_flags & RF_FIRSTSHARE) {
519 			s->r_flags |= RF_FIRSTSHARE;
520 			TAILQ_INSERT_BEFORE(r, s, r_link);
521 			TAILQ_REMOVE(&rm->rm_list, r, r_link);
522 		}
523 
524 		/*
525 		 * Make sure that the sharing list goes away completely
526 		 * if the resource is no longer being shared at all.
527 		 */
528 		if (LIST_NEXT(s, r_sharelink) == 0) {
529 			kfree(s->r_sharehead, M_RMAN);
530 			s->r_sharehead = 0;
531 			s->r_flags &= ~RF_FIRSTSHARE;
532 		}
533 		goto out;
534 	}
535 
536 	/*
537 	 * Look at the adjacent resources in the list and see if our
538 	 * segment can be merged with any of them.
539 	 */
540 	s = TAILQ_PREV(r, resource_head, r_link);
541 	t = TAILQ_NEXT(r, r_link);
542 
543 	if (s != NULL && (s->r_flags & RF_ALLOCATED) == 0
544 	    && t != NULL && (t->r_flags & RF_ALLOCATED) == 0) {
545 		/*
546 		 * Merge all three segments.
547 		 */
548 		s->r_end = t->r_end;
549 		TAILQ_REMOVE(&rm->rm_list, r, r_link);
550 		TAILQ_REMOVE(&rm->rm_list, t, r_link);
551 		kfree(t, M_RMAN);
552 	} else if (s != NULL && (s->r_flags & RF_ALLOCATED) == 0) {
553 		/*
554 		 * Merge previous segment with ours.
555 		 */
556 		s->r_end = r->r_end;
557 		TAILQ_REMOVE(&rm->rm_list, r, r_link);
558 	} else if (t != NULL && (t->r_flags & RF_ALLOCATED) == 0) {
559 		/*
560 		 * Merge next segment with ours.
561 		 */
562 		t->r_start = r->r_start;
563 		TAILQ_REMOVE(&rm->rm_list, r, r_link);
564 	} else {
565 		/*
566 		 * At this point, we know there is nothing we
567 		 * can potentially merge with, because on each
568 		 * side, there is either nothing there or what is
569 		 * there is still allocated.  In that case, we don't
570 		 * want to remove r from the list; we simply want to
571 		 * change it to an unallocated region and return
572 		 * without freeing anything.
573 		 */
574 		r->r_flags &= ~RF_ALLOCATED;
575 		return 0;
576 	}
577 
578 out:
579 	kfree(r, M_RMAN);
580 	return 0;
581 }
582 
583 int
584 rman_release_resource(struct resource *r)
585 {
586 	struct	rman *rm = r->r_rm;
587 	int	rv;
588 
589 	lwkt_gettoken(rm->rm_slock);
590 	rv = int_rman_release_resource(rm, r);
591 	lwkt_reltoken(rm->rm_slock);
592 	return (rv);
593 }
594 
595 uint32_t
596 rman_make_alignment_flags(uint32_t size)
597 {
598 	int	i;
599 
600 	/*
601 	 * Find the hightest bit set, and add one if more than one bit
602 	 * set.  We're effectively computing the ceil(log2(size)) here.
603 	 */
604 	for (i = 32; i > 0; i--)
605 		if ((1 << i) & size)
606 			break;
607 	if (~(1 << i) & size)
608 		i++;
609 
610 	return(RF_ALIGNMENT_LOG2(i));
611 }
612 
613 /*
614  * Sysctl interface for scanning the resource lists.
615  *
616  * We take two input parameters; the index into the list of resource
617  * managers, and the resource offset into the list.
618  */
619 static int
620 sysctl_rman(SYSCTL_HANDLER_ARGS)
621 {
622 	int			*name = (int *)arg1;
623 	u_int			namelen = arg2;
624 	int			rman_idx, res_idx;
625 	struct rman		*rm;
626 	struct resource		*res;
627 	struct u_rman		urm;
628 	struct u_resource	ures;
629 	int			error;
630 
631 	if (namelen != 3)
632 		return (EINVAL);
633 
634 	if (bus_data_generation_check(name[0]))
635 		return (EINVAL);
636 	rman_idx = name[1];
637 	res_idx = name[2];
638 
639 	/*
640 	 * Find the indexed resource manager
641 	 */
642 	TAILQ_FOREACH(rm, &rman_head, rm_link) {
643 		if (rman_idx-- == 0)
644 			break;
645 	}
646 	if (rm == NULL)
647 		return (ENOENT);
648 
649 	/*
650 	 * If the resource index is -1, we want details on the
651 	 * resource manager.
652 	 */
653 	if (res_idx == -1) {
654 		urm.rm_handle = (uintptr_t)rm;
655 		strlcpy(urm.rm_descr, rm->rm_descr, RM_TEXTLEN);
656 		urm.rm_start = rm->rm_start;
657 		urm.rm_size = rm->rm_end - rm->rm_start + 1;
658 		urm.rm_type = rm->rm_type;
659 
660 		error = SYSCTL_OUT(req, &urm, sizeof(urm));
661 		return (error);
662 	}
663 
664 	/*
665 	 * Find the indexed resource and return it.
666 	 */
667 	TAILQ_FOREACH(res, &rm->rm_list, r_link) {
668 		if (res_idx-- == 0) {
669 			ures.r_handle = (uintptr_t)res;
670 			ures.r_parent = (uintptr_t)res->r_rm;
671 			ures.r_device = (uintptr_t)res->r_dev;
672 			if (res->r_dev != NULL) {
673 				if (device_get_name(res->r_dev) != NULL) {
674 					ksnprintf(ures.r_devname, RM_TEXTLEN,
675 					    "%s%d",
676 					    device_get_name(res->r_dev),
677 					    device_get_unit(res->r_dev));
678 				} else {
679 					strlcpy(ures.r_devname, "nomatch",
680 					    RM_TEXTLEN);
681 				}
682 			} else {
683 				ures.r_devname[0] = '\0';
684 			}
685 			ures.r_start = res->r_start;
686 			ures.r_size = res->r_end - res->r_start + 1;
687 			ures.r_flags = res->r_flags;
688 
689 			error = SYSCTL_OUT(req, &ures, sizeof(ures));
690 			return (error);
691 		}
692 	}
693 	return (ENOENT);
694 }
695 
696 SYSCTL_NODE(_hw_bus, OID_AUTO, rman, CTLFLAG_RD, sysctl_rman,
697     "kernel resource manager");
698