text: /* 
   * Copyright (c) 2008, XenSource Inc.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *     * Redistributions of source code must retain the above copyright
   *       notice, this list of conditions and the following disclaimer.
   *     * 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.
   *     * Neither the name of XenSource Inc. nor the names of its contributors
   *       may be used to endorse or promote products derived from this software
   *       without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER
   * 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.
   */
  
  /* log.h: API for writelog communication */
  
  #ifndef __LOG_H__
  #define __LOG_H__ 1
  
  #include <inttypes.h>
  
  #define LOGCMD_SHMP  "shmp"
  #define LOGCMD_PEEK  "peek"
  #define LOGCMD_CLEAR "clrw"
  #define LOGCMD_GET   "getw"
  #define LOGCMD_KICK  "kick"
  
  #define CTLRSPLEN_SHMP  256
  #define CTLRSPLEN_PEEK  4
  #define CTLRSPLEN_CLEAR 4
  #define CTLRSPLEN_GET   4
  #define CTLRSPLEN_KICK  0
  
  /* shmregion is arbitrarily capped at 8 megs for a minimum of
   * 64 MB of data per read (if there are no contiguous regions)
   * In the off-chance that there is more dirty data, multiple
   * reads must be done */
  #define SHMSIZE (8 * 1024 * 1024)
  #define SRINGSIZE 4096
  
  /* The shared memory region is split up into 3 subregions:
   * The first half is reserved for the dirty bitmap log.
   * The second half begins with 1 page for read request descriptors,
   * followed by a big area for supplying read data.
   */
  static inline void* bmstart(void* shm)
  {
    return shm;
  }
  
  static inline void* bmend(void* shm)
  {
    return shm + SHMSIZE/2;
  }
  
  static inline void* sringstart(void* shm)
  {
    return bmend(shm);
  }
  
  static inline void* sdatastart(void* shm)
  {
    return sringstart(shm) + SRINGSIZE;
  }
  
  static inline void* sdataend(void* shm)
  {
    return shm + SHMSIZE;
  }
  
  /* format for messages between log client and server */
  struct log_ctlmsg {
    char msg[4];
    char params[16];
  };
  
  /* extent descriptor */
  struct disk_range {
    uint64_t sector;
    uint32_t count;
  };
  
  /* dirty write logging space. This is an extent ring at the front,
   * full of disk_ranges plus a pointer into the data area */
  /* I think I'd rather have the header in front of each data section to
   * avoid having two separate spaces that can run out, but then I'd either
   * lose page alignment on the data blocks or spend an entire page on the
   * header */
  
  struct log_extent {
    uint64_t sector;
    uint32_t count;
    uint32_t offset; /* offset from start of data area to start of extent */
  };
  
  /* struct above should be 16 bytes, or 256 extents/page */
  
  typedef struct log_extent log_request_t;
  typedef struct log_extent log_response_t;
  
  DEFINE_RING_TYPES(log, log_request_t, log_response_t);
  
  #define LOG_HEADER_PAGES 4
  
  #endif
  