text: /*
   * Copyright 1998 Massachusetts Institute of Technology
   *
   * Permission to use, copy, modify, and distribute this software and
   * its documentation for any purpose and without fee is hereby
   * granted, provided that both the above copyright notice and this
   * permission notice appear in all copies, that both the above
   * copyright notice and this permission notice appear in all
   * supporting documentation, and that the name of M.I.T. not be used
   * in advertising or publicity pertaining to distribution of the
   * software without specific, written prior permission.  M.I.T. makes
   * no representations about the suitability of this software for any
   * purpose.  It is provided "as is" without express or implied
   * warranty.
   * 
   * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
   * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
   * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * $FreeBSD: src/sys/kern/subr_rman.c,v 1.10.2.1 2001/06/05 08:06:08 imp Exp $
   */
  
  /*
   * The kernel resource manager.  This code is responsible for keeping track
   * of hardware resources which are apportioned out to various drivers.
   * It does not actually assign those resources, and it is not expected
   * that end-device drivers will call into this code directly.  Rather,
   * the code which implements the buses that those devices are attached to,
   * and the code which manages CPU resources, will call this code, and the
   * end-device drivers will make upcalls to that code to actually perform
   * the allocation.
   *
   * There are two sorts of resources managed by this code.  The first is
   * the more familiar array (RMAN_ARRAY) type; resources in this class
   * consist of a sequence of individually-allocatable objects which have
   * been numbered in some well-defined order.  Most of the resources
   * are of this type, as it is the most familiar.  The second type is
   * called a gauge (RMAN_GAUGE), and models fungible resources (i.e.,
   * resources in which each instance is indistinguishable from every
   * other instance).  The principal anticipated application of gauges
   * is in the context of power consumption, where a bus may have a specific
   * power budget which all attached devices share.  RMAN_GAUGE is not
   * implemented yet.
   *
   * For array resources, we make one simplifying assumption: two clients
   * sharing the same resource must use the same range of indices.  That
   * is to say, sharing of overlapping-but-not-identical regions is not
   * permitted.
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/kernel.h>
  #include <sys/lock.h>
  #include <sys/malloc.h>
  #include <sys/bus.h>		/* XXX debugging */
  #include <sys/rman.h>
  #include <sys/sysctl.h>
  
  static int rman_debug = 0;
  TUNABLE_INT("debug.rman_debug", &rman_debug);
  SYSCTL_INT(_debug, OID_AUTO, rman_debug, CTLFLAG_RW,
      &rman_debug, 0, "rman debug");
  
  #define DPRINTF(params) if (rman_debug) kprintf params
  
  static MALLOC_DEFINE(M_RMAN, "rman", "Resource manager");
  
  TAILQ_HEAD(rman_head, rman);
  static struct rman_head rman_head;
  static struct lwkt_token rman_tok;	/* mutex to protect rman_head */
  static int int_rman_activate_resource(struct rman *rm, struct resource *r,
  				       struct resource **whohas);
  static int int_rman_deactivate_resource(struct resource *r);
  static int int_rman_release_resource(struct rman *rm, struct resource *r);
  
  int
  rman_init(struct rman *rm, int cpuid)
  {
  	static int once;
  
  	if (once == 0) {
  		once = 1;
  		TAILQ_INIT(&rman_head);
  		lwkt_token_init(&rman_tok, "rman");
  	}
  
  	if (rm->rm_type == RMAN_UNINIT)
  		panic("rman_init");
  	if (rm->rm_type == RMAN_GAUGE)
  		panic("implement RMAN_GAUGE");
  
  	TAILQ_INIT(&rm->rm_list);
  	rm->rm_slock = kmalloc(sizeof *rm->rm_slock, M_RMAN, M_NOWAIT);
  	if (rm->rm_slock == NULL)
  		return ENOMEM;
  	lwkt_token_init(rm->rm_slock, "rmanslock");
  
  	rm->rm_cpuid = cpuid;
  	rm->rm_hold = 0;
  
  	lwkt_gettoken(&rman_tok);
  	TAILQ_INSERT_TAIL(&rman_head, rm, rm_link);
  	lwkt_reltoken(&rman_tok);
  
  	return 0;
  }
  
  /*
   * NB: this interface is not robust against programming errors which
   * add multiple copies of the same region.
   */
  int
  rman_manage_region(struct rman *rm, u_long start, u_long end)
  {
  	struct resource *r, *s;
  
  	DPRINTF(("rman_manage_region: <%s> request: start %#lx, end %#lx\n",
  	    rm->rm_descr, start, end));
  	r = kmalloc(sizeof *r, M_RMAN, M_NOWAIT | M_ZERO);
  	if (r == NULL)
  		return ENOMEM;
  	r->r_sharehead = 0;
  	r->r_start = start;
  	r->r_end = end;
  	r->r_flags = 0;
  	r->r_dev = 0;
  	r->r_rm = rm;
  
  	lwkt_gettoken(rm->rm_slock);
  	for (s = TAILQ_FIRST(&rm->rm_list);
  	     s && s->r_end < r->r_start;
  	     s = TAILQ_NEXT(s, r_link))
  		;
  
  	if (s == NULL)
  		TAILQ_INSERT_TAIL(&rm->rm_list, r, r_link);
  	else
  		TAILQ_INSERT_BEFORE(s, r, r_link);
  
  	lwkt_reltoken(rm->rm_slock);
  	return 0;
  }
  
  int
  rman_fini(struct rman *rm)
  {
  	struct resource *r;
  
  	/*
  	 * All resources must already have been deallocated.
  	 */
  	lwkt_gettoken(rm->rm_slock);
  	TAILQ_FOREACH(r, &rm->rm_list, r_link) {
  		if (r->r_flags & RF_ALLOCATED) {
  			lwkt_reltoken(rm->rm_slock);
  			return EBUSY;
  		}
  	}
  
  	/*
  	 * Protected list removal.  Once removed, wait for any temporary
  	 * holds to be dropped before actually destroying the resource.
  	 */
  	lwkt_gettoken(&rman_tok);
  	TAILQ_REMOVE(&rman_head, rm, rm_link);
  	lwkt_reltoken(&rman_tok);
  
  	if (rm->rm_hold) {
  		kprintf("debug: rman_fini(): rm_hold race fixed on %s\n",
  			rm->rm_descr);
  		while (rm->rm_hold)
  			tsleep(rm, 0, "rmfree", 2);
  	}
  
  	/*
  	 * Destroy all elements remaining on rm_list
  	 */
  	while ((r = TAILQ_FIRST(&rm->rm_list)) != NULL) {
  		TAILQ_REMOVE(&rm->rm_list, r, r_link);
  		kfree(r, M_RMAN);
  	}
  	lwkt_reltoken(rm->rm_slock);
  
  	/*
  	 * Final cleanup
  	 */
  	lwkt_token_uninit(rm->rm_slock);
  	kfree(rm->rm_slock, M_RMAN);
  	rm->rm_slock = NULL;
  
  	return 0;
  }
  
  struct resource *
  rman_reserve_resource(struct rman *rm, u_long start, u_long end, u_long count,
  		      u_int flags, device_t dev)
  {
  	u_int	want_activate;
  	struct	resource *r, *s, *rv;
  	u_long	rstart, rend;
  
  	rv = NULL;
  
  	DPRINTF(("rman_reserve_resource: <%s> request: [%#lx, %#lx], length "
  	       "%#lx, flags %u, device %s\n", rm->rm_descr, start, end,
  	       count, flags,
  	       dev == NULL ? "<null>" : device_get_nameunit(dev)));
  	want_activate = (flags & RF_ACTIVE);
  	flags &= ~RF_ACTIVE;
  
  	lwkt_gettoken(rm->rm_slock);
  
  	for (r = TAILQ_FIRST(&rm->rm_list);
  	     r && r->r_end < start + count - 1;
  	     r = TAILQ_NEXT(r, r_link))
  		;
  
  	if (r == NULL) {
  		DPRINTF(("could not find a region\n"));
  		goto out;
  	}
  
  	/*
  	 * First try to find an acceptable totally-unshared region.
  	 */
  	for (s = r; s; s = TAILQ_NEXT(s, r_link)) {
  		DPRINTF(("considering [%#lx, %#lx]\n", s->r_start, s->r_end));
  		if (s->r_start > end - (count - 1)) {
  			DPRINTF(("s->r_start (%#lx) > end (%#lx)\n",
  			    s->r_start, end));
  			break;
  		}
  		if (s->r_flags & RF_ALLOCATED) {
  			DPRINTF(("region is allocated\n"));
  			continue;
  		}
  		rstart = ulmax(s->r_start, start);
  		rstart = rounddown2(rstart + (1ul << RF_ALIGNMENT(flags)) - 1,
  		    1ul << RF_ALIGNMENT(flags));
  		rend = ulmin(s->r_end, ulmax(start + count - 1, end));
  		DPRINTF(("truncated region: [%#lx, %#lx]; size %#lx (requested %#lx)\n",
  		       rstart, rend, (rend - rstart + 1), count));
  
  		if ((rend - rstart + 1) >= count) {
  			DPRINTF(("candidate region: [%#lx, %#lx], size %#lx\n",
  			       rstart, rend, (rend - rstart + 1)));
  			if ((s->r_end - s->r_start + 1) == count) {
  				DPRINTF(("candidate region is entire chunk\n"));
  				rv = s;
  				rv->r_flags |= RF_ALLOCATED | flags;
  				rv->r_dev = dev;
  				goto out;
  			}
  
  			/*
  			 * If s->r_start < rstart and
  			 *    s->r_end > rstart + count - 1, then
  			 * we need to split the region into three pieces
  			 * (the middle one will get returned to the user).
  			 * Otherwise, we are allocating at either the
  			 * beginning or the end of s, so we only need to
  			 * split it in two.  The first case requires
  			 * two new allocations; the second requires but one.
  			 */
  			rv = kmalloc(sizeof *rv, M_RMAN, M_NOWAIT | M_ZERO);
  			if (rv == NULL)
  				goto out;
  			rv->r_start = rstart;
  			rv->r_end = rstart + count - 1;
  			rv->r_flags = flags | RF_ALLOCATED;
  			rv->r_dev = dev;
  			rv->r_sharehead = 0;
  			rv->r_rm = rm;
  			
  			if (s->r_start < rv->r_start && s->r_end > rv->r_end) {
  				DPRINTF(("splitting region in three parts: "
  				       "[%#lx, %#lx]; [%#lx, %#lx]; [%#lx, %#lx]\n",
  				       s->r_start, rv->r_start - 1,
  				       rv->r_start, rv->r_end,
  				       rv->r_end + 1, s->r_end));
  				/*
  				 * We are allocating in the middle.
  				 */
  				r = kmalloc(sizeof *r, M_RMAN,
  				    M_NOWAIT | M_ZERO);
  				if (r == NULL) {
  					kfree(rv, M_RMAN);
  					rv = NULL;
  					goto out;
  				}
  				r->r_start = rv->r_end + 1;
  				r->r_end = s->r_end;
  				r->r_flags = s->r_flags;
  				r->r_dev = 0;
  				r->r_sharehead = 0;
  				r->r_rm = rm;
  				s->r_end = rv->r_start - 1;
  				TAILQ_INSERT_AFTER(&rm->rm_list, s, rv,
  						     r_link);
  				TAILQ_INSERT_AFTER(&rm->rm_list, rv, r,
  						     r_link);
  			} else if (s->r_start == rv->r_start) {
  				DPRINTF(("allocating from the beginning\n"));
  				/*
  				 * We are allocating at the beginning.
  				 */
  				s->r_start = rv->r_end + 1;
  				TAILQ_INSERT_BEFORE(s, rv, r_link);
  			} else {
  				DPRINTF(("allocating at the end\n"));
  				/*
  				 * We are allocating at the end.
  				 */
  				s->r_end = rv->r_start - 1;
  				TAILQ_INSERT_AFTER(&rm->rm_list, s, rv,
  						     r_link);
  			}
  			goto out;
  		}
  	}
  
  	/*
  	 * Now find an acceptable shared region, if the client's requirements
  	 * allow sharing.  By our implementation restriction, a candidate
  	 * region must match exactly by both size and sharing type in order
  	 * to be considered compatible with the client's request.  (The
  	 * former restriction could probably be lifted without too much
  	 * additional work, but this does not seem warranted.)
  	 */
  	DPRINTF(("no unshared regions found\n"));
  	if ((flags & (RF_SHAREABLE | RF_TIMESHARE)) == 0)
  		goto out;
  
  	for (s = r; s; s = TAILQ_NEXT(s, r_link)) {
  		if (s->r_start > end)
  			break;
  		if ((s->r_flags & flags) != flags)
  			continue;
  		rstart = ulmax(s->r_start, start);
  		rend = ulmin(s->r_end, ulmax(start + count, end));
  		if (s->r_start >= start && s->r_end <= end
  		    && (s->r_end - s->r_start + 1) == count) {
  			rv = kmalloc(sizeof *rv, M_RMAN, M_NOWAIT | M_ZERO);
  			if (rv == NULL)
  				goto out;
  			rv->r_start = s->r_start;
  			rv->r_end = s->r_end;
  			rv->r_flags = s->r_flags & 
  				(RF_ALLOCATED | RF_SHAREABLE | RF_TIMESHARE);
  			rv->r_dev = dev;
  			rv->r_rm = rm;
  			if (s->r_sharehead == 0) {
  				s->r_sharehead = kmalloc(sizeof *s->r_sharehead,
  							M_RMAN,
  							M_NOWAIT | M_ZERO);
  				if (s->r_sharehead == 0) {
  					kfree(rv, M_RMAN);
  					rv = NULL;
  					goto out;
  				}
  				LIST_INIT(s->r_sharehead);
  				LIST_INSERT_HEAD(s->r_sharehead, s, 
  						 r_sharelink);
  				s->r_flags |= RF_FIRSTSHARE;
  			}
  			rv->r_sharehead = s->r_sharehead;
  			LIST_INSERT_HEAD(s->r_sharehead, rv, r_sharelink);
  			goto out;
  		}
  	}
  
  	/*
  	 * We couldn't find anything.
  	 */
  	DPRINTF(("no region found\n"));
  out:
  	/*
  	 * If the user specified RF_ACTIVE in the initial flags,
  	 * which is reflected in `want_activate', we attempt to atomically
  	 * activate the resource.  If this fails, we release the resource
  	 * and indicate overall failure.  (This behavior probably doesn't
  	 * make sense for RF_TIMESHARE-type resources.)
  	 */
  	if (rv && want_activate) {
  		struct resource *whohas;
  		DPRINTF(("activating region\n"));
  		if (int_rman_activate_resource(rm, rv, &whohas)) {
  			int_rman_release_resource(rm, rv);
  			rv = NULL;
  		}
  	}
  	lwkt_reltoken(rm->rm_slock);
  	return (rv);
  }
  
  static int
  int_rman_activate_resource(struct rman *rm, struct resource *r,
  			   struct resource **whohas)
  {
  	struct resource *s;
  	int ok;
  
  	/*
  	 * If we are not timesharing, then there is nothing much to do.
  	 * If we already have the resource, then there is nothing at all to do.
  	 * If we are not on a sharing list with anybody else, then there is
  	 * little to do.
  	 */
  	if ((r->r_flags & RF_TIMESHARE) == 0
  	    || (r->r_flags & RF_ACTIVE) != 0
  	    || r->r_sharehead == 0) {
  		r->r_flags |= RF_ACTIVE;
  		return 0;
  	}
  
  	ok = 1;
  	for (s = LIST_FIRST(r->r_sharehead); s && ok;
  	     s = LIST_NEXT(s, r_sharelink)) {
  		if ((s->r_flags & RF_ACTIVE) != 0) {
  			ok = 0;
  			*whohas = s;
  		}
  	}
  	if (ok) {
  		r->r_flags |= RF_ACTIVE;
  		return 0;
  	}
  	return EBUSY;
  }
  
  int
  rman_activate_resource(struct resource *r)
  {
  	int rv;
  	struct resource *whohas;
  	struct rman *rm;
  
  	rm = r->r_rm;
  	lwkt_gettoken(rm->rm_slock);
  	rv = int_rman_activate_resource(rm, r, &whohas);
  	lwkt_reltoken(rm->rm_slock);
  	return rv;
  }
  
  #if 0
  
  /* XXX */
  int
  rman_await_resource(struct resource *r, int slpflags, int timo)
  {
  	int	rv;
  	struct	resource *whohas;
  	struct	rman *rm;
  
  	rm = r->r_rm;
  	for (;;) {
  		lwkt_gettoken(rm->rm_slock);
  		rv = int_rman_activate_resource(rm, r, &whohas);
  		if (rv != EBUSY)
  			return (rv);	/* returns with ilock held */
  
  		if (r->r_sharehead == 0)
  			panic("rman_await_resource");
  		/*
  		 * A critical section will hopefully will prevent a race 
  		 * between lwkt_reltoken and tsleep where a process
  		 * could conceivably get in and release the resource
  		 * before we have a chance to sleep on it. YYY
  		 */
  		crit_enter();
  		whohas->r_flags |= RF_WANTED;
  		rv = tsleep(r->r_sharehead, slpflags, "rmwait", timo);
  		if (rv) {
  			lwkt_reltoken(rm->rm_slock);
  			crit_exit();
  			return rv;
  		}
  		crit_exit();
  	}
  }
  
  #endif
  
  static int
  int_rman_deactivate_resource(struct resource *r)
  {
  	r->r_flags &= ~RF_ACTIVE;
  	if (r->r_flags & RF_WANTED) {
  		r->r_flags &= ~RF_WANTED;
  		wakeup(r->r_sharehead);
  	}
  	return 0;
  }
  
  int
  rman_deactivate_resource(struct resource *r)
  {
  	struct rman *rm;
  
  	rm = r->r_rm;
  	lwkt_gettoken(rm->rm_slock);
  	int_rman_deactivate_resource(r);
  	lwkt_reltoken(rm->rm_slock);
  	return 0;
  }
  
  static int
  int_rman_release_resource(struct rman *rm, struct resource *r)
  {
  	struct	resource *s, *t;
  
  	if (r->r_flags & RF_ACTIVE)
  		int_rman_deactivate_resource(r);
  
  	/*
  	 * Check for a sharing list first.  If there is one, then we don't
  	 * have to think as hard.
  	 */
  	if (r->r_sharehead) {
  		/*
  		 * If a sharing list exists, then we know there are at
  		 * least two sharers.
  		 *
  		 * If we are in the main circleq, appoint someone else.
  		 */
  		LIST_REMOVE(r, r_sharelink);
  		s = LIST_FIRST(r->r_sharehead);
  		if (r->r_flags & RF_FIRSTSHARE) {
  			s->r_flags |= RF_FIRSTSHARE;
  			TAILQ_INSERT_BEFORE(r, s, r_link);
  			TAILQ_REMOVE(&rm->rm_list, r, r_link);
  		}
  
  		/*
  		 * Make sure that the sharing list goes away completely
  		 * if the resource is no longer being shared at all.
  		 */
  		if (LIST_NEXT(s, r_sharelink) == 0) {
  			kfree(s->r_sharehead, M_RMAN);
  			s->r_sharehead = 0;
  			s->r_flags &= ~RF_FIRSTSHARE;
  		}
  		goto out;
  	}
  
  	/*
  	 * Look at the adjacent resources in the list and see if our
  	 * segment can be merged with any of them.
  	 */
  	s = TAILQ_PREV(r, resource_head, r_link);
  	t = TAILQ_NEXT(r, r_link);
  
  	if (s != NULL && (s->r_flags & RF_ALLOCATED) == 0
  	    && t != NULL && (t->r_flags & RF_ALLOCATED) == 0) {
  		/*
  		 * Merge all three segments.
  		 */
  		s->r_end = t->r_end;
  		TAILQ_REMOVE(&rm->rm_list, r, r_link);
  		TAILQ_REMOVE(&rm->rm_list, t, r_link);
  		kfree(t, M_RMAN);
  	} else if (s != NULL && (s->r_flags & RF_ALLOCATED) == 0) {
  		/*
  		 * Merge previous segment with ours.
  		 */
  		s->r_end = r->r_end;
  		TAILQ_REMOVE(&rm->rm_list, r, r_link);
  	} else if (t != NULL && (t->r_flags & RF_ALLOCATED) == 0) {
  		/*
  		 * Merge next segment with ours.
  		 */
  		t->r_start = r->r_start;
  		TAILQ_REMOVE(&rm->rm_list, r, r_link);
  	} else {
  		/*
  		 * At this point, we know there is nothing we
  		 * can potentially merge with, because on each
  		 * side, there is either nothing there or what is
  		 * there is still allocated.  In that case, we don't
  		 * want to remove r from the list; we simply want to
  		 * change it to an unallocated region and return
  		 * without freeing anything.
  		 */
  		r->r_flags &= ~RF_ALLOCATED;
  		return 0;
  	}
  
  out:
  	kfree(r, M_RMAN);
  	return 0;
  }
  
  int
  rman_release_resource(struct resource *r)
  {
  	struct	rman *rm = r->r_rm;
  	int	rv;
  
  	lwkt_gettoken(rm->rm_slock);
  	rv = int_rman_release_resource(rm, r);
  	lwkt_reltoken(rm->rm_slock);
  	return (rv);
  }
  
  /*
   * Find the hightest bit set, and add one if more than one bit
   * set.  We're effectively computing the ceil(log2(size)) here.
   *
   * This function cannot compute alignments above (1LU<<63)+1
   * as this would require returning '64' which will not fit in
   * the flags field and doesn't work well for calculations either.
   */
  uint32_t
  rman_make_alignment_flags(size_t size)
  {
  	int i;
  
  	for (i = 63; i; --i) {
  		if ((1LU << i) & size)
  			break;
  	}
  	if (~(1LU << i) & size)
  		++i;
  	if (i == 64)
  		i = 63;
  	return(RF_ALIGNMENT_LOG2(i));
  }
  
  /*
   * Sysctl interface for scanning the resource lists.
   *
   * We take two input parameters; the index into the list of resource
   * managers, and the resource offset into the list.
   */
  static int
  sysctl_rman(SYSCTL_HANDLER_ARGS)
  {
  	int			*name = (int *)arg1;
  	u_int			namelen = arg2;
  	int			rman_idx, res_idx;
  	struct rman		*rm;
  	struct resource		*res;
  	struct u_rman		urm;
  	struct u_resource	ures;
  	int			error;
  
  	if (namelen != 3)
  		return (EINVAL);
  
  	if (bus_data_generation_check(name[0]))
  		return (EINVAL);
  	rman_idx = name[1];
  	res_idx = name[2];
  
  	/*
  	 * Find the indexed resource manager
  	 */
  	error = ENOENT;
  	lwkt_gettoken(&rman_tok);
  
  	TAILQ_FOREACH(rm, &rman_head, rm_link) {
  		if (rman_idx-- == 0)
  			break;
  	}
  	if (rm == NULL)
  		goto done;
  
  	/*
  	 * If the resource index is -1, we want details on the
  	 * resource manager.
  	 */
  	if (res_idx == -1) {
  		urm.rm_handle = (uintptr_t)rm;
  		strlcpy(urm.rm_descr, rm->rm_descr, RM_TEXTLEN);
  		urm.rm_start = rm->rm_start;
  		urm.rm_size = rm->rm_end - rm->rm_start + 1;
  		urm.rm_type = rm->rm_type;
  
  		error = SYSCTL_OUT(req, &urm, sizeof(urm));
  		goto done;
  	}
  
  	/*
  	 * Find the indexed resource and return it.
  	 */
  	atomic_add_int(&rm->rm_hold, 1);	/* temp prevent destruction */
  	lwkt_gettoken(rm->rm_slock);
  
  	TAILQ_FOREACH(res, &rm->rm_list, r_link) {
  		if (res_idx-- == 0) {
  			ures.r_handle = (uintptr_t)res;
  			ures.r_parent = (uintptr_t)res->r_rm;
  			ures.r_device = (uintptr_t)res->r_dev;
  			if (res->r_dev != NULL) {
  				if (device_get_name(res->r_dev) != NULL) {
  					ksnprintf(ures.r_devname, RM_TEXTLEN,
  					    "%s%d",
  					    device_get_name(res->r_dev),
  					    device_get_unit(res->r_dev));
  				} else {
  					strlcpy(ures.r_devname, "nomatch",
  					    RM_TEXTLEN);
  				}
  			} else {
  				ures.r_devname[0] = '\0';
  			}
  			ures.r_start = res->r_start;
  			ures.r_size = res->r_end - res->r_start + 1;
  			ures.r_flags = res->r_flags;
  
  			error = SYSCTL_OUT(req, &ures, sizeof(ures));
  			break;
  		}
  	}
  	lwkt_reltoken(rm->rm_slock);
  	atomic_add_int(&rm->rm_hold, -1);
  done:
  	lwkt_reltoken(&rman_tok);
  
  	return (ENOENT);
  }
  
  SYSCTL_NODE(_hw_bus, OID_AUTO, rman, CTLFLAG_RD, sysctl_rman,
      "kernel resource manager");
  