text: /*-
   * This header is BSD licensed so anyone can use the definitions to implement
   * compatible drivers/servers.
   *
   * 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. Neither the name of IBM 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 IBM 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.
   *
   * $FreeBSD$
   */
  
  #ifndef _VIRTIO_BLK_H
  #define _VIRTIO_BLK_H
  
  /* Feature bits */
  #define VIRTIO_BLK_F_BARRIER	0x0001	/* Does host support barriers? */
  #define VIRTIO_BLK_F_SIZE_MAX	0x0002	/* Indicates maximum segment size */
  #define VIRTIO_BLK_F_SEG_MAX	0x0004	/* Indicates maximum # of segments */
  #define VIRTIO_BLK_F_GEOMETRY	0x0010	/* Legacy geometry available  */
  #define VIRTIO_BLK_F_RO		0x0020	/* Disk is read-only */
  #define VIRTIO_BLK_F_BLK_SIZE	0x0040	/* Block size of disk is available*/
  #define VIRTIO_BLK_F_SCSI	0x0080	/* Supports scsi command passthru */
  #define VIRTIO_BLK_F_FLUSH	0x0200	/* Cache flush command support */
  #define VIRTIO_BLK_F_TOPOLOGY	0x0400	/* Topology information is available */
  
  #define VIRTIO_BLK_ID_BYTES	20	/* ID string length */
  
  struct virtio_blk_config {
  	/* The capacity (in 512-byte sectors). */
  	uint64_t capacity;
  	/* The maximum segment size (if VIRTIO_BLK_F_SIZE_MAX) */
  	uint32_t size_max;
  	/* The maximum number of segments (if VIRTIO_BLK_F_SEG_MAX) */
  	uint32_t seg_max;
  	/* geometry the device (if VIRTIO_BLK_F_GEOMETRY) */
  	struct virtio_blk_geometry {
  		uint16_t cylinders;
  		uint8_t heads;
  		uint8_t sectors;
  	} geometry;
  
  	/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
  	uint32_t blk_size;
  } _PACKED;
  
  /*
   * Command types
   *
   * Usage is a bit tricky as some bits are used as flags and some are not.
   *
   * Rules:
   *   VIRTIO_BLK_T_OUT may be combined with VIRTIO_BLK_T_SCSI_CMD or
   *   VIRTIO_BLK_T_BARRIER.  VIRTIO_BLK_T_FLUSH is a command of its own
   *   and may not be combined with any of the other flags.
   */
  
  /* These two define direction. */
  #define VIRTIO_BLK_T_IN		0
  #define VIRTIO_BLK_T_OUT	1
  
  /* This bit says it's a scsi command, not an actual read or write. */
  #define VIRTIO_BLK_T_SCSI_CMD	2
  
  /* Cache flush command */
  #define VIRTIO_BLK_T_FLUSH	4
  
  /* Get device ID command */
  #define VIRTIO_BLK_T_GET_ID	8
  
  /* Barrier before this op. */
  #define VIRTIO_BLK_T_BARRIER	0x80000000
  
  /* ID string length */
  #define VIRTIO_BLK_ID_BYTES	20
  
  /* This is the first element of the read scatter-gather list. */
  struct virtio_blk_outhdr {
  	/* VIRTIO_BLK_T* */
  	uint32_t type;
  	/* io priority. */
  	uint32_t ioprio;
  	/* Sector (ie. 512 byte offset) */
  	uint64_t sector;
  };
  
  struct virtio_scsi_inhdr {
  	uint32_t errors;
  	uint32_t data_len;
  	uint32_t sense_len;
  	uint32_t residual;
  };
  
  /* And this is the final byte of the write scatter-gather list. */
  #define VIRTIO_BLK_S_OK		0
  #define VIRTIO_BLK_S_IOERR	1
  #define VIRTIO_BLK_S_UNSUPP	2
  
  #endif /* _VIRTIO_BLK_H */
  