/*
 * 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.
 *
 *	$Id: subr_rman.c,v 1.1 1998/10/29 01:48:36 wollman 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/lock.h>
#include <sys/malloc.h>
#include <sys/rman.h>
#include <sys/bus.h>		/* XXX debugging */

MALLOC_DEFINE(M_RMAN, "rman", "Resource manager");

struct	rman_head rman_head;
static	struct simplelock rman_lock; /* mutex to protect rman_head */
static	int int_rman_activate_resource(struct rman *rm, struct resource *r,
				       struct resource **whohas);
static	int int_rman_release_resource(struct rman *rm, struct resource *r);

#define	CIRCLEQ_TERMCOND(var, head)	(var == (void *)&(head))

int
rman_init(struct rman *rm)
{
	static int once;
	struct resource *r;

	if (once == 0) {
		once = 1;
		TAILQ_INIT(&rman_head);
		simple_lock_init(&rman_lock);
	}

	if (rm->rm_type == RMAN_UNINIT)
		panic("rman_init");
	if (rm->rm_type == RMAN_GAUGE)
		panic("implement RMAN_GAUGE");

	CIRCLEQ_INIT(&rm->rm_list);
	rm->rm_slock = malloc(sizeof *rm->rm_slock, M_RMAN, M_NOWAIT);
	if (rm->rm_slock == 0)
		return ENOMEM;
	simple_lock_init(rm->rm_slock);

	simple_lock(&rman_lock);
	TAILQ_INSERT_TAIL(&rman_head, rm, rm_link);
	simple_unlock(&rman_lock);
	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;

	r = malloc(sizeof *r, M_RMAN, M_NOWAIT);
	if (r == 0)
		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;

	simple_lock(rm->rm_slock);
	for (s = rm->rm_list.cqh_first;	
	     !CIRCLEQ_TERMCOND(s, rm->rm_list) && s->r_end < r->r_start;
	     s = s->r_link.cqe_next)
		;

	if (CIRCLEQ_TERMCOND(s, rm->rm_list)) {
		CIRCLEQ_INSERT_TAIL(&rm->rm_list, r, r_link);
	} else {
		CIRCLEQ_INSERT_BEFORE(&rm->rm_list, s, r, r_link);
	}

	simple_unlock(rm->rm_slock);
	return 0;
}

int
rman_fini(struct rman *rm)
{
	struct resource *r;

	simple_lock(rm->rm_slock);
	for (r = rm->rm_list.cqh_first;	!CIRCLEQ_TERMCOND(r, rm->rm_list);
	     r = r->r_link.cqe_next) {
		if (r->r_flags & RF_ALLOCATED)
			return EBUSY;
	}

	/*
	 * There really should only be one of these if we are in this
	 * state and the code is working properly, but it can't hurt.
	 */
	for (r = rm->rm_list.cqh_first;	!CIRCLEQ_TERMCOND(r, rm->rm_list);
	     r = rm->rm_list.cqh_first) {
		CIRCLEQ_REMOVE(&rm->rm_list, r, r_link);
		free(r, M_RMAN);
	}
	simple_unlock(rm->rm_slock);
	simple_lock(&rman_lock);
	TAILQ_REMOVE(&rman_head, rm, rm_link);
	simple_unlock(&rman_lock);
	free(rm->rm_slock, M_RMAN);

	return 0;
}

struct resource *
rman_reserve_resource(struct rman *rm, u_long start, u_long end, u_long count,
		      u_int flags, struct device *dev)
{
	u_int	want_activate;
	struct	resource *r, *s, *rv;
	u_long	rstart, rend;

	rv = 0;

#ifdef RMAN_DEBUG
	printf("rman_reserve_resource: <%s> request: [%#lx, %#lx], length "
	       "%#lx, flags %u, device %s%d\n", rm->rm_descr, start, end,
	       count, flags, device_get_name(dev), device_get_unit(dev));
#endif /* RMAN_DEBUG */
	want_activate = (flags & RF_ACTIVE);
	flags &= ~RF_ACTIVE;

	simple_lock(rm->rm_slock);

	for (r = rm->rm_list.cqh_first; 
	     !CIRCLEQ_TERMCOND(r, rm->rm_list) && r->r_end < start;
	     r = r->r_link.cqe_next)
		;

	if (CIRCLEQ_TERMCOND(r, rm->rm_list)) {
#ifdef RMAN_DEBUG
		printf("could not find a region\n");
#endif RMAN_DEBUG
		goto out;
	}

	/*
	 * First try to find an acceptable totally-unshared region.
	 */
	for (s = r; !CIRCLEQ_TERMCOND(s, rm->rm_list);
	     s = s->r_link.cqe_next) {
#ifdef RMAN_DEBUG
		printf("considering [%#lx, %#lx]\n", s->r_start, s->r_end);
#endif /* RMAN_DEBUG */
		if (s->r_start > end) {
#ifdef RMAN_DEBUG
			printf("s->r_start (%#lx) > end (%#lx)\n", s->r_start, end);
#endif /* RMAN_DEBUG */
			break;
		}
		if (s->r_flags & RF_ALLOCATED) {
#ifdef RMAN_DEBUG
			printf("region is allocated\n");
#endif /* RMAN_DEBUG */
			continue;
		}
		rstart = max(s->r_start, start);
		rend = min(s->r_end, max(start + count, end));
#ifdef RMAN_DEBUG
		printf("truncated region: [%#lx, %#lx]; size %#lx (requested %#lx)\n",
		       rstart, rend, (rend - rstart + 1), count);
#endif /* RMAN_DEBUG */

		if ((rend - rstart + 1) >= count) {
#ifdef RMAN_DEBUG
			printf("candidate region: [%#lx, %#lx], size %#lx\n",
			       rend, rstart, (rend - rstart + 1));
#endif /* RMAN_DEBUG */
			if ((s->r_end - s->r_start + 1) == count) {
#ifdef RMAN_DEBUG
				printf("candidate region is entire chunk\n");
#endif /* RMAN_DEBUG */
				rv = s;
				rv->r_flags |= RF_ALLOCATED;
				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 = malloc(sizeof *r, M_RMAN, M_NOWAIT);
			if (rv == 0)
				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;
			
			if (s->r_start < rv->r_start && s->r_end > rv->r_end) {
#ifdef RMAN_DEBUG
				printf("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);
#endif /* RMAN_DEBUG */
				/*
				 * We are allocating in the middle.
				 */
				r = malloc(sizeof *r, M_RMAN, M_NOWAIT);
				if (r == 0) {
					free(rv, M_RMAN);
					rv = 0;
					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;
				s->r_end = rv->r_start - 1;
				CIRCLEQ_INSERT_AFTER(&rm->rm_list, s, rv,
						     r_link);
				CIRCLEQ_INSERT_AFTER(&rm->rm_list, rv, r,
						     r_link);
			} else if (s->r_start == rv->r_start) {
#ifdef RMAN_DEBUG
				printf("allocating from the beginning\n");
#endif /* RMAN_DEBUG */
				/*
				 * We are allocating at the beginning.
				 */
				s->r_start = rv->r_end + 1;
				CIRCLEQ_INSERT_BEFORE(&rm->rm_list, s, rv,
						      r_link);
			} else {
#ifdef RMAN_DEBUG
				printf("allocating at the end\n");
#endif /* RMAN_DEBUG */
				/*
				 * We are allocating at the end.
				 */
				s->r_end = rv->r_start - 1;
				CIRCLEQ_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.)
	 */
#ifdef RMAN_DEBUG
	printf("no unshared regions found\n");
#endif /* RMAN_DEBUG */
	if ((flags & (RF_SHAREABLE | RF_TIMESHARE)) == 0)
		goto out;

	for (s = r; !CIRCLEQ_TERMCOND(s, rm->rm_list);
	     s = s->r_link.cqe_next) {
		if (s->r_start > end)
			break;
		if ((s->r_flags & flags) != flags)
			continue;
		rstart = max(s->r_start, start);
		rend = min(s->r_end, max(start + count, end));
		if (s->r_start >= start && s->r_end <= end
		    && (s->r_end - s->r_start + 1) == count) {
			rv = malloc(sizeof *rv, M_RMAN, M_NOWAIT);
			if (rv == 0)
				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 = malloc(sizeof *s->r_sharehead,
							M_RMAN, M_NOWAIT);
				if (s->r_sharehead == 0) {
					free(rv, M_RMAN);
					rv = 0;
					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.
	 */
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;
		if (int_rman_activate_resource(rm, rv, &whohas)) {
			int_rman_release_resource(rm, rv);
			rv = 0;
		}
	}
			
	simple_unlock(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 = r->r_sharehead->lh_first; s && ok;
	     s = s->r_sharelink.le_next) {
		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;
	simple_lock(rm->rm_slock);
	rv = int_rman_activate_resource(rm, r, &whohas);
	simple_unlock(rm->rm_slock);
	return rv;
}

int
rman_await_resource(struct resource *r, int pri, int timo)
{
	int	rv, s;
	struct	resource *whohas;
	struct	rman *rm;

	rm = r->r_rm;
	for (;;) {
		simple_lock(rm->rm_slock);
		rv = int_rman_activate_resource(rm, r, &whohas);
		if (rv != EBUSY)
			return (rv);

		if (r->r_sharehead == 0)
			panic("rman_await_resource");
		/*
		 * splhigh hopefully will prevent a race between
		 * simple_unlock and tsleep where a process
		 * could conceivably get in and release the resource
		 * before we have a chance to sleep on it.
		 */
		s = splhigh();
		whohas->r_flags |= RF_WANTED;
		simple_unlock(rm->rm_slock);
		rv = tsleep(r->r_sharehead, pri, "rmwait", timo);
		if (rv) {
			splx(s);
			return rv;
		}
		simple_lock(rm->rm_slock);
		splx(s);
	}
}

int
rman_deactivate_resource(struct resource *r)
{
	struct	rman *rm;

	rm = r->r_rm;
	simple_lock(rm->rm_slock);
	r->r_flags &= ~RF_ACTIVE;
	if (r->r_flags & RF_WANTED) {
		r->r_flags &= ~RF_WANTED;
		wakeup(r->r_sharehead);
	}
	simple_unlock(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)
		return EBUSY;

	/*
	 * 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 = r->r_sharehead->lh_first;
		if (r->r_flags & RF_FIRSTSHARE) {
			s->r_flags |= RF_FIRSTSHARE;
			CIRCLEQ_INSERT_BEFORE(&rm->rm_list, r, s, r_link);
			CIRCLEQ_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 (s->r_sharelink.le_next == 0) {
			free(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 = r->r_link.cqe_prev;
	t = r->r_link.cqe_next;

	if (s != (void *)&rm->rm_list && (s->r_flags & RF_ALLOCATED) == 0
	    && t != (void *)&rm->rm_list && (t->r_flags & RF_ALLOCATED) == 0) {
		/*
		 * Merge all three segments.
		 */
		s->r_end = t->r_end;
		CIRCLEQ_REMOVE(&rm->rm_list, r, r_link);
		CIRCLEQ_REMOVE(&rm->rm_list, t, r_link);
		free(t, M_RMAN);
	} else if (s != (void *)&rm->rm_list
		   && (s->r_flags & RF_ALLOCATED) == 0) {
		/*
		 * Merge previous segment with ours.
		 */
		s->r_end = r->r_end;
		CIRCLEQ_REMOVE(&rm->rm_list, r, r_link);
	} else if (t != (void *)&rm->rm_list
		   && (t->r_flags & RF_ALLOCATED) == 0) {
		/*
		 * Merge next segment with ours.
		 */
		t->r_start = r->r_start;
		CIRCLEQ_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:
	free(r, M_RMAN);
	return 0;
}

int
rman_release_resource(struct resource *r)
{
	int	rv;
	struct	rman *rm = r->r_rm;

	simple_lock(rm->rm_slock);
	rv = int_rman_release_resource(rm, r);
	simple_unlock(rm->rm_slock);
	return (rv);
}
