text: /*-
   * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   * All rights reserved.
   *
   * 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``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 THE AUTHORS OR CONTRIBUTORS 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.
   */
  
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: src/sys/geom/zero/g_zero.c,v 1.4 2006/02/01 12:06:01 pjd Exp $");
  
  #include <sys/param.h>
  #include <sys/bio.h>
  #include <sys/kernel.h>
  #include <sys/limits.h>
  #include <sys/malloc.h>
  #include <sys/queue.h>
  #include <sys/sysctl.h>
  #include <sys/systm.h>
  
  #include <geom/geom.h>
  
  
  #define	G_ZERO_CLASS_NAME	"ZERO"
  
  SYSCTL_DECL(_kern_geom);
  SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW, 0, "GEOM_ZERO stuff");
  static int g_zero_clear = 1;
  SYSCTL_INT(_kern_geom_zero, OID_AUTO, clear, CTLFLAG_RW, &g_zero_clear, 0,
      "Clear read data buffer");
  static int g_zero_byte = 0;
  SYSCTL_INT(_kern_geom_zero, OID_AUTO, byte, CTLFLAG_RW, &g_zero_byte, 0,
      "Byte (octet) value to clear the buffers with");
  
  static void
  g_zero_start(struct bio *bp)
  {
  	int error = ENXIO;
  
  	switch (bp->bio_cmd) {
  	case BIO_READ:
  		if (g_zero_clear)
  			memset(bp->bio_data, g_zero_byte, bp->bio_length);
  		/* FALLTHROUGH */
  	case BIO_DELETE:
  	case BIO_WRITE:
  		bp->bio_completed = bp->bio_length;
  		error = 0;
  		break;
  	case BIO_GETATTR:
  	default:
  		error = EOPNOTSUPP;
  		break;
  	}
  	g_io_deliver(bp, error);
  }
  
  static void
  g_zero_init(struct g_class *mp)
  {
  	struct g_geom *gp;
  	struct g_provider *pp;
  
  	g_topology_assert();
  	gp = g_new_geomf(mp, "gzero");
  	gp->start = g_zero_start;
  	gp->access = g_std_access;
  	pp = g_new_providerf(gp, "%s", gp->name);
  	pp->mediasize = 1152921504606846976LLU;
  	pp->sectorsize = 512;
  	g_error_provider(pp, 0);
  }
  
  static int
  g_zero_destroy_geom(struct gctl_req *req __unused, struct g_class *mp __unused,
      struct g_geom *gp)
  {
  	struct g_provider *pp;
  
  	g_topology_assert();
  	if (gp == NULL)
  		return (0);
  	pp = LIST_FIRST(&gp->provider);
  	if (pp == NULL)
  		return (0);
  	if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
  		return (EBUSY);
  	g_wither_geom(gp, ENXIO);
  	return (EBUSY);
  }
  
  static struct g_class g_zero_class = {
  	.name = G_ZERO_CLASS_NAME,
  	.version = G_VERSION,
  	.init = g_zero_init,
  	.destroy_geom = g_zero_destroy_geom
  };
  
  DECLARE_GEOM_CLASS(g_zero_class, g_zero);
  