#ifndef _SCSI_SCSI_TCQ_H
  #define _SCSI_SCSI_TCQ_H
  
  #include <linux/blkdev.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_device.h>

  #include <scsi/scsi_host.h>

  #define MSG_SIMPLE_TAG	0x20
  #define MSG_HEAD_TAG	0x21
  #define MSG_ORDERED_TAG	0x22

  #define MSG_ACA_TAG	0x24	/* unsupported */

  
  #define SCSI_NO_TAG	(-1)    /* identify no tag in use */

  #ifdef CONFIG_BLOCK

  
  /**
   * scsi_get_tag_type - get the type of tag the device supports
   * @sdev:	the scsi device
   *
   * Notes:
   *	If the drive only supports simple tags, returns MSG_SIMPLE_TAG
   *	if it supports all tag types, returns MSG_ORDERED_TAG.
   */
  static inline int scsi_get_tag_type(struct scsi_device *sdev)
  {
  	if (!sdev->tagged_supported)
  		return 0;
  	if (sdev->ordered_tags)
  		return MSG_ORDERED_TAG;
  	if (sdev->simple_tags)
  		return MSG_SIMPLE_TAG;
  	return 0;
  }
  
  static inline void scsi_set_tag_type(struct scsi_device *sdev, int tag)
  {
  	switch (tag) {
  	case MSG_ORDERED_TAG:
  		sdev->ordered_tags = 1;
  		/* fall through */
  	case MSG_SIMPLE_TAG:
  		sdev->simple_tags = 1;
  		break;
  	case 0:
  		/* fall through */
  	default:
  		sdev->ordered_tags = 0;
  		sdev->simple_tags = 0;
  		break;
  	}
  }
  /**
   * scsi_activate_tcq - turn on tag command queueing
   * @SDpnt:	device to turn on TCQ for
   * @depth:	queue depth
   *
   * Notes:
   *	Eventually, I hope depth would be the maximum depth
   *	the device could cope with and the real queue depth
   *	would be adjustable from 0 to depth.
   **/
  static inline void scsi_activate_tcq(struct scsi_device *sdev, int depth)
  {
  	if (!sdev->tagged_supported)
  		return;
  
  	if (!blk_queue_tagged(sdev->request_queue))

  		blk_queue_init_tags(sdev->request_queue, depth,
  				    sdev->host->bqt);

  
  	scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
  }
  
  /**
   * scsi_deactivate_tcq - turn off tag command queueing
   * @SDpnt:	device to turn off TCQ for
   **/
  static inline void scsi_deactivate_tcq(struct scsi_device *sdev, int depth)
  {
  	if (blk_queue_tagged(sdev->request_queue))
  		blk_queue_free_tags(sdev->request_queue);
  	scsi_adjust_queue_depth(sdev, 0, depth);
  }
  
  /**
   * scsi_populate_tag_msg - place a tag message in a buffer
   * @SCpnt:	pointer to the Scsi_Cmnd for the tag
   * @msg:	pointer to the area to place the tag
   *
   * Notes:
   *	designed to create the correct type of tag message for the 
   *	particular request.  Returns the size of the tag message.
   *	May return 0 if TCQ is disabled for this device.
   **/
  static inline int scsi_populate_tag_msg(struct scsi_cmnd *cmd, char *msg)
  {
          struct request *req = cmd->request;

  
          if (blk_rq_tagged(req)) {

  		*msg++ = MSG_SIMPLE_TAG;

          	*msg++ = req->tag;
          	return 2;
  	}
  
  	return 0;
  }
  
  /**
   * scsi_find_tag - find a tagged command by device
   * @SDpnt:	pointer to the ScSI device
   * @tag:	the tag number
   *
   * Notes:
   *	Only works with tags allocated by the generic blk layer.
   **/
  static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
  {
  
          struct request *req;
  
          if (tag != SCSI_NO_TAG) {
          	req = blk_queue_find_tag(sdev->request_queue, tag);
  	        return req ? (struct scsi_cmnd *)req->special : NULL;
  	}
  
  	/* single command, look in space */
  	return sdev->current_cmnd;
  }

  /**
   * scsi_init_shared_tag_map - create a shared tag map
   * @shost:	the host to share the tag map among all devices
   * @depth:	the total depth of the map
   */

  static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)

  {

  	/*
  	 * If the shared tag map isn't already initialized, do it now.
  	 * This saves callers from having to check ->bqt when setting up
  	 * devices on the shared host (for libata)
  	 */
  	if (!shost->bqt) {
  		shost->bqt = blk_init_tags(depth);
  		if (!shost->bqt)
  			return -ENOMEM;
  	}
  
  	return 0;

  }

  /**
   * scsi_host_find_tag - find the tagged command by host
   * @shost:	pointer to scsi_host
   * @tag:	tag of the scsi_cmnd
   *
   * Notes:
   *	Only works with tags allocated by the generic blk layer.
   **/
  static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
  						int tag)
  {
  	struct request *req;
  
  	if (tag != SCSI_NO_TAG) {
  		req = blk_map_queue_find_tag(shost->bqt, tag);
  		return req ? (struct scsi_cmnd *)req->special : NULL;
  	}
  	return NULL;
  }

  #endif /* CONFIG_BLOCK */

  #endif /* _SCSI_SCSI_TCQ_H */