/*      $NetBSD: dmover_backend.c,v 1.9 2011/05/14 18:24:47 jakllsch Exp $      */

/*
* Copyright (c) 2002 Wasabi Systems, Inc.
* All rights reserved.
*
* Written by Jason R. Thorpe for Wasabi Systems, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed for the NetBSD Project by
*      Wasabi Systems, Inc.
* 4. The name of Wasabi Systems, Inc. may not be used to endorse
*    or promote products derived from this software without specific prior
*    written permission.
*
* THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
* 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.
*/

/*
* dmover_backend.c: Backend management functions for dmover-api.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: dmover_backend.c,v 1.9 2011/05/14 18:24:47 jakllsch Exp $");

#include <sys/param.h>
#include <sys/mutex.h>
#include <sys/systm.h>
#include <sys/once.h>

#include <dev/dmover/dmovervar.h>

TAILQ_HEAD(, dmover_backend) dmover_backend_list;
kmutex_t dmover_backend_list_lock;
static bool initialized;

static int
initialize(void)
{

       KASSERT(initialized == false);

       TAILQ_INIT(&dmover_backend_list);
       mutex_init(&dmover_backend_list_lock, MUTEX_DEFAULT, IPL_VM);

       /* Initialize the other bits of dmover. */
       dmover_session_initialize();
       dmover_request_initialize();
       dmover_process_initialize();

       initialized = true;

       return 0;
}

/*
* dmover_backend_register:     [back-end interface function]
*
*      Register a back-end with dmover-api.
*/
void
dmover_backend_register(struct dmover_backend *dmb)
{
       static ONCE_DECL(control);

       RUN_ONCE(&control, initialize);

       KASSERT(initialized == true);

       LIST_INIT(&dmb->dmb_sessions);
       dmb->dmb_nsessions = 0;

       TAILQ_INIT(&dmb->dmb_pendreqs);
       dmb->dmb_npendreqs = 0;

       mutex_enter(&dmover_backend_list_lock);
       TAILQ_INSERT_TAIL(&dmover_backend_list, dmb, dmb_list);
       mutex_exit(&dmover_backend_list_lock);
}

/*
* dmover_backend_unregister:   [back-end interface function]
*
*      Un-register a back-end from dmover-api.
*/
void
dmover_backend_unregister(struct dmover_backend *dmb)
{

       KASSERT(initialized == true);

       /* XXX */
       if (dmb->dmb_nsessions)
               panic("dmover_backend_unregister");

       mutex_enter(&dmover_backend_list_lock);
       TAILQ_REMOVE(&dmover_backend_list, dmb, dmb_list);
       mutex_exit(&dmover_backend_list_lock);
}

/*
* dmover_backend_alloc:
*
*      Allocate and return a back-end on behalf of a session.
*/
int
dmover_backend_alloc(struct dmover_session *dses, const char *type)
{
       struct dmover_backend *dmb, *best_dmb = NULL;
       const struct dmover_algdesc *algdesc, *best_algdesc = NULL;

       if (__predict_false(initialized == false)) {
               return (ESRCH);
       }

       mutex_enter(&dmover_backend_list_lock);

       /* First, find a back-end that can handle the session parts. */
       for (dmb = TAILQ_FIRST(&dmover_backend_list); dmb != NULL;
            dmb = TAILQ_NEXT(dmb, dmb_list)) {
               /*
                * First, check to see if the back-end supports the
                * function we wish to perform.
                */
               algdesc = dmover_algdesc_lookup(dmb->dmb_algdescs,
                   dmb->dmb_nalgdescs, type);
               if (algdesc == NULL)
                       continue;

               if (best_dmb == NULL) {
                       best_dmb = dmb;
                       best_algdesc = algdesc;
                       continue;
               }

               /*
                * XXX All the stuff from here on should be shot in
                * XXX the head.  Instead, we should build a list
                * XXX of candidates, and select the best back-end
                * XXX when a request is scheduled for processing.
                */

               if (dmb->dmb_speed >= best_dmb->dmb_speed) {
                       /*
                        * If the current best match is slower than
                        * this back-end, then this one is the new
                        * best match.
                        */
                       if (dmb->dmb_speed > best_dmb->dmb_speed) {
                               best_dmb = dmb;
                               best_algdesc = algdesc;
                               continue;
                       }

                       /*
                        * If this back-end has fewer sessions allocated
                        * to it than the current best match, then this
                        * one is now the best match.
                        */
                       if (best_dmb->dmb_nsessions > dmb->dmb_nsessions) {
                               best_dmb = dmb;
                               best_algdesc = algdesc;
                               continue;
                       }
               }
       }
       if (best_dmb == NULL) {
               mutex_exit(&dmover_backend_list_lock);
               return (ESRCH);
       }

       KASSERT(best_algdesc != NULL);

       /* Plug the back-end into the static (XXX) assignment. */
       dses->__dses_assignment.das_backend = best_dmb;
       dses->__dses_assignment.das_algdesc = best_algdesc;

       dses->dses_ninputs = best_algdesc->dad_ninputs;

       LIST_INSERT_HEAD(&best_dmb->dmb_sessions, dses, __dses_list);
       best_dmb->dmb_nsessions++;

       mutex_exit(&dmover_backend_list_lock);

       return (0);
}

/*
* dmover_backend_release:
*
*      Release the back-end from the specified session.
*/
void
dmover_backend_release(struct dmover_session *dses)
{
       struct dmover_backend *dmb;

       mutex_enter(&dmover_backend_list_lock);

       /* XXX Clear out the static assignment. */
       dmb = dses->__dses_assignment.das_backend;
       dses->__dses_assignment.das_backend = NULL;
       dses->__dses_assignment.das_algdesc = NULL;

       LIST_REMOVE(dses, __dses_list);
       dmb->dmb_nsessions--;

       mutex_exit(&dmover_backend_list_lock);
}

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