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dm_target_zero.c revision 1.29 
      1 /*        $NetBSD: dm_target_zero.c,v 1.29 2019/12/21 11:59:03 tkusumi 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 #include <sys/cdefs.h>
     32 __KERNEL_RCSID(0, "$NetBSD: dm_target_zero.c,v 1.29 2019/12/21 11:59:03 tkusumi Exp $");
     33 
     34 /*
     35  * This file implements initial version of device-mapper zero target.
     36  */
     37 #include <sys/types.h>
     38 #include <sys/param.h>
     39 #include <sys/buf.h>
     40 
     41 #include "dm.h"
     42 
     43 #ifdef DM_TARGET_MODULE
     44 /*
     45  * Every target can be compiled directly to dm driver or as a
     46  * separate module this part of target is used for loading targets
     47  * to dm driver.
     48  * Target can be unloaded from kernel only if there are no users of
     49  * it e.g. there are no devices which uses that target.
     50  */
     51 #include <sys/kernel.h>
     52 #include <sys/module.h>
     53 
     54 MODULE(MODULE_CLASS_MISC, dm_target_zero, "dm");
     55 
     56 static int
     57 dm_target_zero_modcmd(modcmd_t cmd, void *arg)
     58 {
     59 	dm_target_t *dmt;
     60 	int r;
     61 
     62 	switch (cmd) {
     63 	case MODULE_CMD_INIT:
     64 		if ((dmt = dm_target_lookup("zero")) != NULL) {
     65 			dm_target_unbusy(dmt);
     66 			return EEXIST;
     67 		}
     68 		dmt = dm_target_alloc("zero");
     69 
     70 		dmt->version[0] = 1;
     71 		dmt->version[1] = 0;
     72 		dmt->version[2] = 0;
     73 		dmt->init = &dm_target_zero_init;
     74 		dmt->table = &dm_target_zero_table;
     75 		dmt->strategy = &dm_target_zero_strategy;
     76 		dmt->destroy = &dm_target_zero_destroy;
     77 		dmt->upcall = &dm_target_zero_upcall;
     78 
     79 		r = dm_target_insert(dmt);
     80 		break;
     81 
     82 	case MODULE_CMD_FINI:
     83 		r = dm_target_rem("zero");
     84 
     85 		break;
     86 
     87 	case MODULE_CMD_STAT:
     88 		return ENOTTY;
     89 
     90 	default:
     91 		return ENOTTY;
     92 	}
     93 
     94 	return r;
     95 }
     96 #endif
     97 
     98 /*
     99  * Zero target init function. This target doesn't need
    100  * target specific config area.
    101  */
    102 int
    103 dm_target_zero_init(dm_table_entry_t *table_en, int argc, char **argv)
    104 {
    105 
    106 	if (argc != 0) {
    107 		printf("Zero target takes 0 args, %d given\n", argc);
    108 		return EINVAL;
    109 	}
    110 
    111 	printf("Zero target init function called!!\n");
    112 
    113 	table_en->target_config = NULL;
    114 
    115 	return 0;
    116 }
    117 
    118 /* Table routine called to get params string. */
    119 char *
    120 dm_target_zero_table(void *target_config)
    121 {
    122 
    123 	return NULL;
    124 }
    125 
    126 /*
    127  * This routine does IO operations.
    128  */
    129 int
    130 dm_target_zero_strategy(dm_table_entry_t *table_en, struct buf *bp)
    131 {
    132 
    133 	memset(bp->b_data, 0, bp->b_bcount);
    134 	bp->b_resid = 0;	/* nestiobuf_done wants b_resid = 0 to be sure
    135 				 * that there is no other io to done  */
    136 	biodone(bp);
    137 
    138 	return 0;
    139 }
    140 
    141 /* Does not need to do anything here. */
    142 int
    143 dm_target_zero_destroy(dm_table_entry_t *table_en)
    144 {
    145 
    146 	/* Unbusy target so we can unload it */
    147 	dm_target_unbusy(table_en->target);
    148 
    149 	return 0;
    150 }
    151 
    152 /* Unsuported for this target. */
    153 int
    154 dm_target_zero_upcall(dm_table_entry_t *table_en, struct buf *bp)
    155 {
    156 
    157 	return 0;
    158 }
    159