root/include/scsi/scsi_tcq.h

DEFINITIONS

1. scsi_get_tag_type
2. scsi_set_tag_type
3. scsi_activate_tcq
4. scsi_deactivate_tcq
5. scsi_populate_tag_msg
6. scsi_find_tag
7. scsi_init_shared_tag_map
8. scsi_host_find_tag

#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 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;
        struct scsi_device *sdev = cmd->device;

        if (blk_rq_tagged(req)) {
                if (sdev->ordered_tags && req->cmd_flags & REQ_HARDBARRIER)
                        *msg++ = MSG_ORDERED_TAG;
                else
                        *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)
{
        shost->bqt = blk_init_tags(depth);
        return shost->bqt ? 0 : -ENOMEM;
}

/**
 * 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 */