sys/dev/disk/dm/dm_target_zero.c

   1 /*        $NetBSD: dm_target_zero.c,v 1.10 2010/01/04 00:12:22 haad Exp $      */
   2
   3 /*
   4  * Copyright (c) 2008 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Adam Hamsik.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * This file implements initial version of device-mapper zero target.
  34  */
  35 #include <dev/disk/dm/dm.h>
  36
  37 /*
  38  * This routine does IO operations.
  39  */
  40 static int
  41 dm_target_zero_strategy(dm_table_entry_t *table_en, struct buf *bp)
  42 {
  43         memset(bp->b_data, 0, bp->b_bcount);
  44         bp->b_resid = 0;
  45         biodone(&bp->b_bio1);
  46
  47         return 0;
  48 }
  49
  50 static int
  51 dmtz_mod_handler(module_t mod, int type, void *unused)
  52 {
  53         dm_target_t *dmt = NULL;
  54         int err = 0;
  55
  56         switch(type) {
  57         case MOD_LOAD:
  58                 if ((dmt = dm_target_lookup("zero")) != NULL) {
  59                         dm_target_unbusy(dmt);
  60                         return EEXIST;
  61                 }
  62                 dmt = dm_target_alloc("zero");
  63                 dmt->version[0] = 1;
  64                 dmt->version[1] = 0;
  65                 dmt->version[2] = 0;
  66                 dmt->strategy = &dm_target_zero_strategy;
  67
  68                 err = dm_target_insert(dmt);
  69                 if (err == 0)
  70                         kprintf("dm_target_zero: Successfully initialized\n");
  71                 break;
  72
  73         case MOD_UNLOAD:
  74                 err = dm_target_remove("zero");
  75                 if (err == 0)
  76                         kprintf("dm_target_zero: unloaded\n");
  77                 break;
  78         }
  79
  80         return err;
  81 }
  82
  83 DM_TARGET_BUILTIN(dm_target_zero, dmtz_mod_handler);