1/*	$NetBSD: dmover_backend.c,v 1.8 2008/01/05 02:47:03 matt Exp $	*/
2
3/*
4 * Copyright (c) 2002 Wasabi Systems, Inc.
5 * All rights reserved.
6 *
7 * Written by Jason R. Thorpe for Wasabi Systems, Inc.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 *    must display the following acknowledgement:
19 *	This product includes software developed for the NetBSD Project by
20 *	Wasabi Systems, Inc.
21 * 4. The name of Wasabi Systems, Inc. may not be used to endorse
22 *    or promote products derived from this software without specific prior
23 *    written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
27 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
28 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
29 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
31 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
32 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
33 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
34 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35 * POSSIBILITY OF SUCH DAMAGE.
36 */
37
38/*
39 * dmover_backend.c: Backend management functions for dmover-api.
40 */
41
42#include <sys/cdefs.h>
43__KERNEL_RCSID(0, "$NetBSD: dmover_backend.c,v 1.8 2008/01/05 02:47:03 matt Exp $");
44
45#include <sys/param.h>
46#include <sys/mutex.h>
47#include <sys/systm.h>
48#include <sys/once.h>
49
50#include <dev/dmover/dmovervar.h>
51
52TAILQ_HEAD(, dmover_backend) dmover_backend_list;
53kmutex_t dmover_backend_list_lock;
54static bool initialized;
55
56static int
57initialize(void)
58{
59
60	KASSERT(initialized == false);
61
62	TAILQ_INIT(&dmover_backend_list);
63	mutex_init(&dmover_backend_list_lock, MUTEX_DEFAULT, IPL_VM);
64
65	/* Initialize the other bits of dmover. */
66	dmover_session_initialize();
67	dmover_request_initialize();
68	dmover_process_initialize();
69
70	initialized = true;
71
72	return 0;
73}
74
75/*
76 * dmover_backend_register:	[back-end interface function]
77 *
78 *	Register a back-end with dmover-api.
79 */
80void
81dmover_backend_register(struct dmover_backend *dmb)
82{
83	static ONCE_DECL(control);
84
85	RUN_ONCE(&control, initialize);
86
87	KASSERT(initialized == true);
88
89	LIST_INIT(&dmb->dmb_sessions);
90	dmb->dmb_nsessions = 0;
91
92	TAILQ_INIT(&dmb->dmb_pendreqs);
93	dmb->dmb_npendreqs = 0;
94
95	mutex_enter(&dmover_backend_list_lock);
96	TAILQ_INSERT_TAIL(&dmover_backend_list, dmb, dmb_list);
97	mutex_exit(&dmover_backend_list_lock);
98}
99
100/*
101 * dmover_backend_unregister:	[back-end interface function]
102 *
103 *	Un-register a back-end from dmover-api.
104 */
105void
106dmover_backend_unregister(struct dmover_backend *dmb)
107{
108
109	KASSERT(initialized == true);
110
111	/* XXX */
112	if (dmb->dmb_nsessions)
113		panic("dmover_backend_unregister");
114
115	mutex_enter(&dmover_backend_list_lock);
116	TAILQ_REMOVE(&dmover_backend_list, dmb, dmb_list);
117	mutex_exit(&dmover_backend_list_lock);
118}
119
120/*
121 * dmover_backend_alloc:
122 *
123 *	Allocate and return a back-end on behalf of a session.
124 */
125int
126dmover_backend_alloc(struct dmover_session *dses, const char *type)
127{
128	struct dmover_backend *dmb, *best_dmb = NULL;
129	const struct dmover_algdesc *algdesc, *best_algdesc = NULL;
130
131	if (__predict_false(initialized == false)) {
132		return (ESRCH);
133	}
134
135	mutex_enter(&dmover_backend_list_lock);
136
137	/* First, find a back-end that can handle the session parts. */
138	for (dmb = TAILQ_FIRST(&dmover_backend_list); dmb != NULL;
139	     dmb = TAILQ_NEXT(dmb, dmb_list)) {
140		/*
141		 * First, check to see if the back-end supports the
142		 * function we wish to perform.
143		 */
144		algdesc = dmover_algdesc_lookup(dmb->dmb_algdescs,
145		    dmb->dmb_nalgdescs, type);
146		if (algdesc == NULL)
147			continue;
148
149		if (best_dmb == NULL) {
150			best_dmb = dmb;
151			best_algdesc = algdesc;
152			continue;
153		}
154
155		/*
156		 * XXX All the stuff from here on should be shot in
157		 * XXX the head.  Instead, we should build a list
158		 * XXX of candidates, and select the best back-end
159		 * XXX when a request is scheduled for processing.
160		 */
161
162		if (dmb->dmb_speed >= best_dmb->dmb_speed) {
163			/*
164			 * If the current best match is slower than
165			 * this back-end, then this one is the new
166			 * best match.
167			 */
168			if (dmb->dmb_speed > best_dmb->dmb_speed) {
169				best_dmb = dmb;
170				best_algdesc = algdesc;
171				continue;
172			}
173
174			/*
175			 * If this back-end has fewer sessions allocated
176			 * to it than the current best match, then this
177			 * one is now the best match.
178			 */
179			if (best_dmb->dmb_nsessions > dmb->dmb_nsessions) {
180				best_dmb = dmb;
181				best_algdesc = algdesc;
182				continue;
183			}
184		}
185	}
186	if (best_dmb == NULL) {
187		mutex_exit(&dmover_backend_list_lock);
188		return (ESRCH);
189	}
190
191	KASSERT(best_algdesc != NULL);
192
193	/* Plug the back-end into the static (XXX) assignment. */
194	dses->__dses_assignment.das_backend = best_dmb;
195	dses->__dses_assignment.das_algdesc = best_algdesc;
196
197	dses->dses_ninputs = best_algdesc->dad_ninputs;
198
199	LIST_INSERT_HEAD(&best_dmb->dmb_sessions, dses, __dses_list);
200	best_dmb->dmb_nsessions++;
201
202	mutex_exit(&dmover_backend_list_lock);
203
204	return (0);
205}
206
207/*
208 * dmover_backend_release:
209 *
210 *	Release the back-end from the specified session.
211 */
212void
213dmover_backend_release(struct dmover_session *dses)
214{
215	struct dmover_backend *dmb;
216
217	mutex_enter(&dmover_backend_list_lock);
218
219	/* XXX Clear out the static assignment. */
220	dmb = dses->__dses_assignment.das_backend;
221	dses->__dses_assignment.das_backend = NULL;
222	dses->__dses_assignment.das_algdesc = NULL;
223
224	LIST_REMOVE(dses, __dses_list);
225	dmb->dmb_nsessions--;
226
227	mutex_exit(&dmover_backend_list_lock);
228}
229