- Use vfs_readv/vfs_writev instead of direct calls to VFS functions

[mirror/scst/.git] / scst / include / scst.h

/*
 *  include/scst.h
 *
 *  Copyright (C) 2004 - 2009 Vladislav Bolkhovitin <vst@vlnb.net>
 *  Copyright (C) 2004 - 2005 Leonid Stoljar
 *  Copyright (C) 2007 - 2009 ID7 Ltd.
 *
 *  Main SCSI target mid-level include file.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation, version 2
 *  of the License.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 */

#ifndef __SCST_H
#define __SCST_H

#include <linux/types.h>
#include <linux/version.h>
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/wait.h>

#define CONFIG_SCST_PROC

#ifdef CONFIG_SCST_PROC
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#endif

#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi.h>

#include <scst_const.h>

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 19)
#ifndef RHEL_RELEASE_CODE
typedef _Bool bool;
#endif
#define true  1
#define false 0
#endif

#include "scst_sgv.h"

/*
 * Version numbers, the same as for the kernel.
 *
 * Changing it don't forget to change SCST_FIO_REV in scst_vdisk.c
 * and FIO_REV in usr/fileio/common.h as well.
 */
#define SCST_VERSION(a, b, c, d)    (((a) << 24) + ((b) << 16) + ((c) << 8) + d)
#define SCST_VERSION_CODE           SCST_VERSION(2, 0, 0, 0)
#ifdef CONFIG_SCST_PROC
#define SCST_VERSION_STRING_SUFFIX  "-procfs"
#else
#define SCST_VERSION_STRING_SUFFIX
#endif
#define SCST_VERSION_STRING         "2.0.0-pre1" SCST_VERSION_STRING_SUFFIX
#define SCST_INTERFACE_VERSION      \
                SCST_VERSION_STRING "$Revision$" SCST_CONST_VERSION


#if (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 18))
#define COMPLETION_INITIALIZER_ONSTACK(work) \
        ({ init_completion(&work); work; })

/*
 * Lockdep needs to run a non-constant initializer for on-stack
 * completions - so we use the _ONSTACK() variant for those that
 * are on the kernel stack:
 */
#ifdef CONFIG_LOCKDEP
# define DECLARE_COMPLETION_ONSTACK(work) \
        struct completion work = COMPLETION_INITIALIZER_ONSTACK(work)
#else
# define DECLARE_COMPLETION_ONSTACK(work) DECLARE_COMPLETION(work)
#endif

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(const struct list_head *list,
                                const struct list_head *head)
{
        return list->next == head;
}

#endif

#define SCST_LOCAL_NAME                 "scst_lcl_drvr"

/*************************************************************
 ** States of command processing state machine. At first,
 ** "active" states, then - "passive" ones. This is to have
 ** more efficient generated code of the corresponding
 ** "switch" statements.
 *************************************************************/

/* Internal parsing */
#define SCST_CMD_STATE_PRE_PARSE     0

/* Dev handler's parse() is going to be called */
#define SCST_CMD_STATE_DEV_PARSE     1

/* Allocation of the cmd's data buffer */
#define SCST_CMD_STATE_PREPARE_SPACE 2

/* Target driver's rdy_to_xfer() is going to be called */
#define SCST_CMD_STATE_RDY_TO_XFER   3

/* Target driver's pre_exec() is going to be called */
#define SCST_CMD_STATE_TGT_PRE_EXEC  4

/* Cmd is going to be sent for execution */
#define SCST_CMD_STATE_SEND_FOR_EXEC 5

/* Cmd is being checked if it should be executed locally */
#define SCST_CMD_STATE_LOCAL_EXEC    6

/* Cmd is ready for execution */
#define SCST_CMD_STATE_REAL_EXEC     7

/* Internal post-exec checks */
#define SCST_CMD_STATE_PRE_DEV_DONE  8

/* Internal MODE SELECT pages related checks */
#define SCST_CMD_STATE_MODE_SELECT_CHECKS 9

/* Dev handler's dev_done() is going to be called */
#define SCST_CMD_STATE_DEV_DONE      10

/* Target driver's xmit_response() is going to be called */
#define SCST_CMD_STATE_PRE_XMIT_RESP 11

/* Target driver's xmit_response() is going to be called */
#define SCST_CMD_STATE_XMIT_RESP     12

/* Cmd finished */
#define SCST_CMD_STATE_FINISHED      13

/* Internal cmd finished */
#define SCST_CMD_STATE_FINISHED_INTERNAL 14

#define SCST_CMD_STATE_LAST_ACTIVE   (SCST_CMD_STATE_FINISHED_INTERNAL+100)

/* A cmd is created, but scst_cmd_init_done() not called */
#define SCST_CMD_STATE_INIT_WAIT     (SCST_CMD_STATE_LAST_ACTIVE+1)

/* LUN translation (cmd->tgt_dev assignment) */
#define SCST_CMD_STATE_INIT          (SCST_CMD_STATE_LAST_ACTIVE+2)

/* Allocation of the cmd's data buffer */
#define SCST_CMD_STATE_PREPROCESS_DONE (SCST_CMD_STATE_LAST_ACTIVE+3)

/* Waiting for data from the initiator (until scst_rx_data() called) */
#define SCST_CMD_STATE_DATA_WAIT     (SCST_CMD_STATE_LAST_ACTIVE+4)

/* Waiting for CDB's execution finish */
#define SCST_CMD_STATE_REAL_EXECUTING (SCST_CMD_STATE_LAST_ACTIVE+5)

/* Waiting for response's transmission finish */
#define SCST_CMD_STATE_XMIT_WAIT     (SCST_CMD_STATE_LAST_ACTIVE+6)

/*************************************************************
 * Can be retuned instead of cmd's state by dev handlers'
 * functions, if the command's state should be set by default
 *************************************************************/
#define SCST_CMD_STATE_DEFAULT        500

/*************************************************************
 * Can be retuned instead of cmd's state by dev handlers'
 * functions, if it is impossible to complete requested
 * task in atomic context. The cmd will be restarted in thread
 * context.
 *************************************************************/
#define SCST_CMD_STATE_NEED_THREAD_CTX 1000

/*************************************************************
 * Can be retuned instead of cmd's state by dev handlers'
 * parse function, if the cmd processing should be stopped
 * for now. The cmd will be restarted by dev handlers itself.
 *************************************************************/
#define SCST_CMD_STATE_STOP           1001

/*************************************************************
 ** States of mgmt command processing state machine
 *************************************************************/

/* LUN translation (mcmd->tgt_dev assignment) */
#define SCST_MCMD_STATE_INIT     0

/* Mgmt cmd is ready for processing */
#define SCST_MCMD_STATE_READY    1

/* Mgmt cmd is being executing */
#define SCST_MCMD_STATE_EXECUTING 2

/* Post check when affected commands done */
#define SCST_MCMD_STATE_POST_AFFECTED_CMDS_DONE 3

/* Target driver's task_mgmt_fn_done() is going to be called */
#define SCST_MCMD_STATE_DONE     4

/* The mcmd finished */
#define SCST_MCMD_STATE_FINISHED 5

/*************************************************************
 ** Constants for "atomic" parameter of SCST's functions
 *************************************************************/
#define SCST_NON_ATOMIC              0
#define SCST_ATOMIC                  1

/*************************************************************
 ** Values for pref_context parameter of scst_cmd_init_done(),
 ** scst_rx_data(), scst_restart_cmd(), scst_tgt_cmd_done()
 ** and scst_cmd_done()
 *************************************************************/

enum scst_exec_context {
        /*
         * Direct cmd's processing (i.e. regular function calls in the current
         * context) sleeping is not allowed
         */
        SCST_CONTEXT_DIRECT_ATOMIC,

        /*
         * Direct cmd's processing (i.e. regular function calls in the current
         * context), sleeping is allowed, no restrictions
         */
        SCST_CONTEXT_DIRECT,

        /* Tasklet or thread context required for cmd's processing */
        SCST_CONTEXT_TASKLET,

        /* Thread context required for cmd's processing */
        SCST_CONTEXT_THREAD,

        /*
         * Context is the same as it was in previous call of the corresponding
         * callback. For example, if dev handler's exec() does sync. data
         * reading this value should be used for scst_cmd_done(). The same is
         * true if scst_tgt_cmd_done() called directly from target driver's
         * xmit_response(). Not allowed in scst_cmd_init_done() and
         * scst_cmd_init_stage1_done().
         */
        SCST_CONTEXT_SAME
};

/*************************************************************
 ** Values for status parameter of scst_rx_data()
 *************************************************************/

/* Success */
#define SCST_RX_STATUS_SUCCESS       0

/*
 * Data receiving finished with error, so set the sense and
 * finish the command, including xmit_response() call
 */
#define SCST_RX_STATUS_ERROR         1

/*
 * Data receiving finished with error and the sense is set,
 * so finish the command, including xmit_response() call
 */
#define SCST_RX_STATUS_ERROR_SENSE_SET 2

/*
 * Data receiving finished with fatal error, so finish the command,
 * but don't call xmit_response()
 */
#define SCST_RX_STATUS_ERROR_FATAL   3

/*************************************************************
 ** Values for status parameter of scst_restart_cmd()
 *************************************************************/

/* Success */
#define SCST_PREPROCESS_STATUS_SUCCESS       0

/*
 * Command's processing finished with error, so set the sense and
 * finish the command, including xmit_response() call
 */
#define SCST_PREPROCESS_STATUS_ERROR         1

/*
 * Command's processing finished with error and the sense is set,
 * so finish the command, including xmit_response() call
 */
#define SCST_PREPROCESS_STATUS_ERROR_SENSE_SET 2

/*
 * Command's processing finished with fatal error, so finish the command,
 * but don't call xmit_response()
 */
#define SCST_PREPROCESS_STATUS_ERROR_FATAL   3

/* Thread context requested */
#define SCST_PREPROCESS_STATUS_NEED_THREAD   4

/*************************************************************
 ** Values for AEN functions
 *************************************************************/

/*
 * SCSI Asynchronous Event. Parameter contains SCSI sense
 * (Unit Attention). AENs generated only for 2 the following UAs:
 * CAPACITY DATA HAS CHANGED and REPORTED LUNS DATA HAS CHANGED.
 * Other UAs reported regularly as CHECK CONDITION status,
 * because it doesn't look safe to report them using AENs, since
 * reporting using AENs opens delivery race windows even in case of
 * untagged commands.
 */
#define SCST_AEN_SCSI                0

/*************************************************************
 ** Allowed return/status codes for report_aen() callback and
 ** scst_set_aen_delivery_status() function
 *************************************************************/

/* Success */
#define SCST_AEN_RES_SUCCESS         0

/* Not supported */
#define SCST_AEN_RES_NOT_SUPPORTED  -1

/* Failure */
#define SCST_AEN_RES_FAILED         -2

/*************************************************************
 ** Allowed return codes for xmit_response(), rdy_to_xfer()
 *************************************************************/

/* Success */
#define SCST_TGT_RES_SUCCESS         0

/* Internal device queue is full, retry again later */
#define SCST_TGT_RES_QUEUE_FULL      -1

/*
 * It is impossible to complete requested task in atomic context.
 * The cmd will be restarted in thread  context.
 */
#define SCST_TGT_RES_NEED_THREAD_CTX -2

/*
 * Fatal error, if returned by xmit_response() the cmd will
 * be destroyed, if by any other function, xmit_response()
 * will be called with HARDWARE ERROR sense data
 */
#define SCST_TGT_RES_FATAL_ERROR     -3

/*************************************************************
 ** Allowed return codes for dev handler's exec()
 *************************************************************/

/* The cmd is done, go to other ones */
#define SCST_EXEC_COMPLETED          0

/* The cmd should be sent to SCSI mid-level */
#define SCST_EXEC_NOT_COMPLETED      1

/*
 * Thread context is required to execute the command.
 * Exec() will be called again in the thread context.
 */
#define SCST_EXEC_NEED_THREAD        2

/*
 * Set if cmd is finished and there is status/sense to be sent.
 * The status should be not sent (i.e. the flag not set) if the
 * possibility to perform a command in "chunks" (i.e. with multiple
 * xmit_response()/rdy_to_xfer()) is used (not implemented yet).
 * Obsolete, use scst_cmd_get_is_send_status() instead.
 */
#define SCST_TSC_FLAG_STATUS         0x2

/*************************************************************
 ** Additional return code for dev handler's task_mgmt_fn()
 *************************************************************/

/* Regular standard actions for the command should be done */
#define SCST_DEV_TM_NOT_COMPLETED     1

/*************************************************************
 ** Session initialization phases
 *************************************************************/

/* Set if session is being initialized */
#define SCST_SESS_IPH_INITING        0

/* Set if the session is successfully initialized */
#define SCST_SESS_IPH_SUCCESS        1

/* Set if the session initialization failed */
#define SCST_SESS_IPH_FAILED         2

/* Set if session is initialized and ready */
#define SCST_SESS_IPH_READY          3

/*************************************************************
 ** Session shutdown phases
 *************************************************************/

/* Set if session is initialized and ready */
#define SCST_SESS_SPH_READY          0

/* Set if session is shutting down */
#define SCST_SESS_SPH_SHUTDOWN       1

/*************************************************************
 ** Session's async (atomic) flags
 *************************************************************/

/* Set if the sess's hw pending work is scheduled */
#define SCST_SESS_HW_PENDING_WORK_SCHEDULED     0

/*************************************************************
 ** Cmd's async (atomic) flags
 *************************************************************/

/* Set if the cmd is aborted and ABORTED sense will be sent as the result */
#define SCST_CMD_ABORTED                0

/* Set if the cmd is aborted by other initiator */
#define SCST_CMD_ABORTED_OTHER          1

/* Set if the cmd is aborted and counted in cmd_done_wait_count */
#define SCST_CMD_DONE_COUNTED           2

/* Set if no response should be sent to the target about this cmd */
#define SCST_CMD_NO_RESP                3

/* Set if the cmd is dead and can be destroyed at any time */
#define SCST_CMD_CAN_BE_DESTROYED       4

/*************************************************************
 ** Tgt_dev's async. flags (tgt_dev_flags)
 *************************************************************/

/* Set if tgt_dev has Unit Attention sense */
#define SCST_TGT_DEV_UA_PENDING         0

/* Set if tgt_dev is RESERVED by another session */
#define SCST_TGT_DEV_RESERVED           1

/* Set if the corresponding context is atomic */
#define SCST_TGT_DEV_AFTER_INIT_WR_ATOMIC       5
#define SCST_TGT_DEV_AFTER_INIT_OTH_ATOMIC      6
#define SCST_TGT_DEV_AFTER_RESTART_WR_ATOMIC    7
#define SCST_TGT_DEV_AFTER_RESTART_OTH_ATOMIC   8
#define SCST_TGT_DEV_AFTER_RX_DATA_ATOMIC       9
#define SCST_TGT_DEV_AFTER_EXEC_ATOMIC          10

#define SCST_TGT_DEV_CLUST_POOL                 11

#ifdef CONFIG_SCST_PROC

/*************************************************************
 ** Name of the entry in /proc
 *************************************************************/
#define SCST_PROC_ENTRY_NAME         "scsi_tgt"

#endif

/*************************************************************
 ** Activities suspending timeout
 *************************************************************/
#define SCST_SUSPENDING_TIMEOUT                 (90 * HZ)

/*************************************************************
 ** Kernel cache creation helper
 *************************************************************/
#ifndef KMEM_CACHE
#define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\
        sizeof(struct __struct), __alignof__(struct __struct),\
        (__flags), NULL, NULL)
#endif

/*************************************************************
 ** Vlaid_mask constants for scst_analyze_sense()
 *************************************************************/

#define SCST_SENSE_KEY_VALID            1
#define SCST_SENSE_ASC_VALID            2
#define SCST_SENSE_ASCQ_VALID           4

#define SCST_SENSE_ASCx_VALID           (SCST_SENSE_ASC_VALID | \
                                         SCST_SENSE_ASCQ_VALID)

#define SCST_SENSE_ALL_VALID            (SCST_SENSE_KEY_VALID | \
                                         SCST_SENSE_ASC_VALID | \
                                         SCST_SENSE_ASCQ_VALID)

/*************************************************************
 *                     TYPES
 *************************************************************/

struct scst_tgt;
struct scst_session;
struct scst_cmd;
struct scst_mgmt_cmd;
struct scst_device;
struct scst_tgt_dev;
struct scst_dev_type;
struct scst_acg;
struct scst_acg_dev;
struct scst_acn;
struct scst_aen;

/*
 * SCST uses 64-bit numbers to represent LUN's internally. The value
 * NO_SUCH_LUN is guaranteed to be different of every valid LUN.
 */
#define NO_SUCH_LUN ((uint64_t)-1)

typedef enum dma_data_direction scst_data_direction;

enum scst_cdb_flags {
        /* SCST_TRANSFER_LEN_TYPE_FIXED must be equiv 1 (FIXED_BIT in cdb) */
        SCST_TRANSFER_LEN_TYPE_FIXED =          0x001,
        SCST_SMALL_TIMEOUT =                    0x002,
        SCST_LONG_TIMEOUT =                     0x004,
        SCST_UNKNOWN_LENGTH =                   0x008,
        SCST_INFO_NOT_FOUND =                   0x010, /* must be single bit */
        SCST_VERIFY_BYTCHK_MISMATCH_ALLOWED =   0x020,
        SCST_IMPLICIT_HQ =                      0x040,
        SCST_SKIP_UA =                          0x080,
        SCST_WRITE_MEDIUM =                     0x100,
        SCST_LOCAL_CMD =                        0x200,
        SCST_LOCAL_EXEC_NEEDED =                0x400,
};

/*
 * Scsi_Target_Template: defines what functions a target driver will
 * have to provide in order to work with the target mid-level.
 * MUST HAVEs define functions that are expected to be in order to work.
 * OPTIONAL says that there is a choice.
 *
 * Also, pay attention to the fact that a command is BLOCKING or NON-BLOCKING.
 * NON-BLOCKING means that a function returns immediately and will not wait
 * for actual data transfer to finish. Blocking in such command could have
 * negative impact on overall system performance. If blocking is necessary,
 * it is worth to consider creating dedicated thread(s) in target driver, to
 * which the commands would be passed and which would perform blocking
 * operations instead of SCST.
 *
 * If the function allowed to sleep or not is determined by its last
 * argument, which is true, if sleeping is not allowed. In this case,
 * if the function requires sleeping, it  can return
 * SCST_TGT_RES_NEED_THREAD_CTX, and it will be recalled in the thread context,
 * where sleeping is allowed.
 */
struct scst_tgt_template {
        /* public: */

        /*
         * SG tablesize allows to check whether scatter/gather can be used
         * or not.
         */
        int sg_tablesize;

        /*
         * True, if this target adapter uses unchecked DMA onto an ISA bus.
         */
        unsigned unchecked_isa_dma:1;

        /*
         * True, if this target adapter can benefit from using SG-vector
         * clustering (i.e. smaller number of segments).
         */
        unsigned use_clustering:1;

        /*
         * True, if this target adapter doesn't support SG-vector clustering
         */
        unsigned no_clustering:1;

        /*
         * True, if corresponding function supports execution in
         * the atomic (non-sleeping) context
         */
        unsigned xmit_response_atomic:1;
        unsigned rdy_to_xfer_atomic:1;

#ifdef CONFIG_SCST_PROC
        /* True, if the template doesn't need the entry in /proc */
        unsigned no_proc_entry:1;
#endif

        /*
         * The maximum time in seconds cmd can stay inside the target
         * hardware, i.e. after rdy_to_xfer() and xmit_response(), before
         * on_hw_pending_cmd_timeout() will be called, if defined.
         *
         * In the current implementation a cmd will be aborted in time t
         * max_hw_pending_time <= t < 2*max_hw_pending_time.
         */
        int max_hw_pending_time;

        /*
         * This function is equivalent to the SCSI
         * queuecommand. The target should transmit the response
         * buffer and the status in the scst_cmd struct.
         * The expectation is that this executing this command is NON-BLOCKING.
         *
         * After the response is actually transmitted, the target
         * should call the scst_tgt_cmd_done() function of the
         * mid-level, which will allow it to free up the command.
         * Returns one of the SCST_TGT_RES_* constants.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * MUST HAVE
         */
        int (*xmit_response) (struct scst_cmd *cmd);

        /*
         * This function informs the driver that data
         * buffer corresponding to the said command have now been
         * allocated and it is OK to receive data for this command.
         * This function is necessary because a SCSI target does not
         * have any control over the commands it receives. Most lower
         * level protocols have a corresponding function which informs
         * the initiator that buffers have been allocated e.g., XFER_
         * RDY in Fibre Channel. After the data is actually received
         * the low-level driver needs to call scst_rx_data() in order to
         * continue processing this command.
         * Returns one of the SCST_TGT_RES_* constants.
         * This command is expected to be NON-BLOCKING.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * OPTIONAL
         */
        int (*rdy_to_xfer) (struct scst_cmd *cmd);

        /*
         * Called if cmd stays inside the target hardware, i.e. after
         * rdy_to_xfer() and xmit_response(), more than max_hw_pending_time
         * time. The target driver supposed to cleanup this command and
         * resume cmd's processing.
         *
         * OPTIONAL
         */
        void (*on_hw_pending_cmd_timeout) (struct scst_cmd *cmd);

        /*
         * Called to notify the driver that the command is about to be freed.
         * Necessary, because for aborted commands xmit_response() could not
         * be called. Could be called on IRQ context.
         *
         * OPTIONAL
         */
        void (*on_free_cmd) (struct scst_cmd *cmd);

        /*
         * This function allows target driver to handle data buffer
         * allocations on its own.
         *
         * Target driver doesn't have to always allocate buffer in this
         * function, but if it decide to do it, it must check that
         * scst_cmd_get_data_buff_alloced() returns 0, otherwise to avoid
         * double buffer allocation and memory leaks alloc_data_buf() shall
         * fail.
         *
         * Shall return 0 in case of success or < 0 (preferrably -ENOMEM)
         * in case of error, or > 0 if the regular SCST allocation should be
         * done. In case of returning successfully,
         * scst_cmd->tgt_data_buf_alloced will be set by SCST.
         *
         * It is possible that both target driver and dev handler request own
         * memory allocation. In this case, data will be memcpy() between
         * buffers, where necessary.
         *
         * If allocation in atomic context - cf. scst_cmd_atomic() - is not
         * desired or fails and consequently < 0 is returned, this function
         * will be re-called in thread context.
         *
         * Please note that the driver will have to handle itself all relevant
         * details such as scatterlist setup, highmem, freeing the allocated
         * memory, etc.
         *
         * OPTIONAL.
         */
        int (*alloc_data_buf) (struct scst_cmd *cmd);

        /*
         * This function informs the driver that data
         * buffer corresponding to the said command have now been
         * allocated and other preprocessing tasks have been done.
         * A target driver could need to do some actions at this stage.
         * After the target driver done the needed actions, it shall call
         * scst_restart_cmd() in order to continue processing this command.
         *
         * Called only if the cmd is queued using scst_cmd_init_stage1_done()
         * instead of scst_cmd_init_done().
         *
         * Returns void, the result is expected to be returned using
         * scst_restart_cmd().
         *
         * This command is expected to be NON-BLOCKING.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * OPTIONAL.
         */
        void (*preprocessing_done) (struct scst_cmd *cmd);

        /*
         * This function informs the driver that the said command is about
         * to be executed.
         *
         * Returns one of the SCST_PREPROCESS_* constants.
         *
         * This command is expected to be NON-BLOCKING.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * OPTIONAL
         */
        int (*pre_exec) (struct scst_cmd *cmd);

        /*
         * This function informs the driver that all affected by the
         * corresponding task management function commands have beed completed.
         * No return value expected.
         *
         * This function is expected to be NON-BLOCKING.
         *
         * Called without any locks held from a thread context.
         *
         * OPTIONAL
         */
        void (*task_mgmt_affected_cmds_done) (struct scst_mgmt_cmd *mgmt_cmd);

        /*
         * This function informs the driver that the corresponding task
         * management function has been completed, i.e. all the corresponding
         * commands completed and freed. No return value expected.
         *
         * This function is expected to be NON-BLOCKING.
         *
         * Called without any locks held from a thread context.
         *
         * MUST HAVE if the target supports task management.
         */
        void (*task_mgmt_fn_done) (struct scst_mgmt_cmd *mgmt_cmd);

        /*
         * This function should detect the target adapters that
         * are present in the system. The function should return a value
         * >= 0 to signify the number of detected target adapters.
         * A negative value should be returned whenever there is
         * an error.
         *
         * MUST HAVE
         */
        int (*detect) (struct scst_tgt_template *tgt_template);

        /*
         * This function should free up the resources allocated to the device.
         * The function should return 0 to indicate successful release
         * or a negative value if there are some issues with the release.
         * In the current version the return value is ignored.
         *
         * MUST HAVE
         */
        int (*release) (struct scst_tgt *tgt);

        /*
         * This function is used for Asynchronous Event Notifications.
         *
         * Returns one of the SCST_AEN_RES_* constants.
         * After AEN is sent, target driver must call scst_aen_done() and,
         * optionally, scst_set_aen_delivery_status().
         *
         * This command is expected to be NON-BLOCKING, but can sleep.
         *
         * MUST HAVE, if low-level protocol supports AENs.
         */
        int (*report_aen) (struct scst_aen *aen);

#ifdef CONFIG_SCST_PROC
        /*
         * Those functions can be used to export the driver's statistics and
         * other infos to the world outside the kernel as well as to get some
         * management commands from it.
         *
         * OPTIONAL
         */
        int (*read_proc) (struct seq_file *seq, struct scst_tgt *tgt);
        int (*write_proc) (char *buffer, char **start, off_t offset,
                int length, int *eof, struct scst_tgt *tgt);
#endif

        /*
         * This function allows to enable or disable particular target.
         * A disabled target doesn't receive and process any SCSI commands.
         *
         * SHOULD HAVE to avoid race when there are connected initiators,
         * while target not yet completed the initial configuration. In this
         * case the too early connected initiators would see not those devices,
         * which they intended to see.
         */
        ssize_t (*enable_tgt) (struct scst_tgt *tgt, const char *buffer,
                           size_t size);

        /*
         * This function shows if particular target is enabled or not.
         *
         * SHOULD HAVE, see above why.
         */
        bool (*is_tgt_enabled) (struct scst_tgt *tgt);

        /*
         * Name of the template. Must be unique to identify
         * the template. MUST HAVE
         */
        const char name[SCST_MAX_NAME];

        /*
         * Number of additional threads to the pool of dedicated threads.
         * Used if xmit_response() or rdy_to_xfer() is blocking.
         * It is the target driver's duty to ensure that not more, than that
         * number of threads, are blocked in those functions at any time.
         */
        int threads_num;

        /* Optional default log flags */
        const unsigned long default_trace_flags;

        /* Optional pointer to trace flags */
        unsigned long *trace_flags;

        /* Optional local trace table */
        struct scst_trace_log *trace_tbl;

        /* Optional local trace table help string */
        const char *trace_tbl_help;

#ifndef CONFIG_SCST_PROC
        /* Optional sysfs attributes */
        const struct attribute **tgtt_attrs;

        /* Optional sysfs target attributes */
        const struct attribute **tgt_attrs;
#endif

        /** Private, must be inited to 0 by memset() **/

        /* List of targets per template, protected by scst_mutex */
        struct list_head tgt_list;

        /* List entry of global templates list */
        struct list_head scst_template_list_entry;

#ifdef CONFIG_SCST_PROC
        /* The pointer to the /proc directory entry */
        struct proc_dir_entry *proc_tgt_root;
#endif

        /* Set if tgtt_kobj was initialized */
        unsigned int tgtt_kobj_initialized:1;

        struct kobject tgtt_kobj; /* kobject for this struct */

        struct completion tgtt_kobj_release_cmpl;

#ifdef CONFIG_SCST_PROC
        /* Device number in /proc */
        int proc_dev_num;
#endif
};

struct scst_dev_type {
        /* SCSI type of the supported device. MUST HAVE */
        int type;

        /*
         * True, if corresponding function supports execution in
         * the atomic (non-sleeping) context
         */
        unsigned parse_atomic:1;
        unsigned exec_atomic:1;
        unsigned dev_done_atomic:1;

#ifdef CONFIG_SCST_PROC
        /* Set, if no /proc files should be automatically created by SCST */
        unsigned no_proc:1;
#endif

        /*
         * Should be set, if exec() is synchronous. This is a hint to SCST core
         * to optimize commands order management.
         */
        unsigned exec_sync:1;

        /*
         * Called to parse CDB from the cmd and initialize
         * cmd->bufflen and cmd->data_direction (both - REQUIRED).
         * Returns the command's next state or SCST_CMD_STATE_DEFAULT,
         * if the next default state should be used, or
         * SCST_CMD_STATE_NEED_THREAD_CTX if the function called in atomic
         * context, but requires sleeping, or SCST_CMD_STATE_STOP if the
         * command should not be further processed for now. In the
         * SCST_CMD_STATE_NEED_THREAD_CTX case the function
         * will be recalled in the thread context, where sleeping is allowed.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * MUST HAVE
         */
        int (*parse) (struct scst_cmd *cmd);

        /*
         * Called to execute CDB. Useful, for instance, to implement
         * data caching. The result of CDB execution is reported via
         * cmd->scst_cmd_done() callback.
         * Returns:
         *  - SCST_EXEC_COMPLETED - the cmd is done, go to other ones
         *  - SCST_EXEC_NEED_THREAD - thread context is required to execute
         *      the command. Exec() will be called again in the thread context.
         *  - SCST_EXEC_NOT_COMPLETED - the cmd should be sent to SCSI
         *      mid-level.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         *
         * If this function provides sync execution, you should set
         * exec_sync flag and consider to setup dedicated threads by
         * setting threads_num > 0.
         *
         * !! If this function is implemented, scst_check_local_events() !!
         * !! shall be called inside it just before the actual command's !!
         * !! execution.                                                 !!
         *
         * OPTIONAL, if not set, the commands will be sent directly to SCSI
         * device.
         */
        int (*exec) (struct scst_cmd *cmd);

        /*
         * Called to notify dev handler about the result of cmd execution
         * and perform some post processing. Cmd's fields is_send_status and
         * resp_data_len should be set by this function, but SCST offers good
         * defaults.
         * Returns the command's next state or SCST_CMD_STATE_DEFAULT,
         * if the next default state should be used, or
         * SCST_CMD_STATE_NEED_THREAD_CTX if the function called in atomic
         * context, but requires sleeping. In the last case, the function
         * will be recalled in the thread context, where sleeping is allowed.
         *
         * Pay attention to "atomic" attribute of the cmd, which can be get
         * by scst_cmd_atomic(): it is true if the function called in the
         * atomic (non-sleeping) context.
         */
        int (*dev_done) (struct scst_cmd *cmd);

        /*
         * Called to notify dev hander that the command is about to be freed.
         * Could be called on IRQ context.
         */
        void (*on_free_cmd) (struct scst_cmd *cmd);

        /*
         * Called to execute a task management command.
         * Returns:
         *  - SCST_MGMT_STATUS_SUCCESS - the command is done with success,
         *      no firther actions required
         *  - The SCST_MGMT_STATUS_* error code if the command is failed and
         *      no further actions required
         *  - SCST_DEV_TM_NOT_COMPLETED - regular standard actions for the
         *      command should be done
         *
         * Called without any locks held from a thread context.
         */
        int (*task_mgmt_fn) (struct scst_mgmt_cmd *mgmt_cmd,
                struct scst_tgt_dev *tgt_dev);

        /*
         * Called when new device is attaching to the dev handler
         * Returns 0 on success, error code otherwise.
         */
        int (*attach) (struct scst_device *dev);

        /* Called when new device is detaching from the dev handler */
        void (*detach) (struct scst_device *dev);

        /*
         * Called when new tgt_dev (session) is attaching to the dev handler.
         * Returns 0 on success, error code otherwise.
         */
        int (*attach_tgt) (struct scst_tgt_dev *tgt_dev);

        /* Called when tgt_dev (session) is detaching from the dev handler */
        void (*detach_tgt) (struct scst_tgt_dev *tgt_dev);

#ifdef CONFIG_SCST_PROC
        /*
         * Those functions can be used to export the handler's statistics and
         * other infos to the world outside the kernel as well as to get some
         * management commands from it.
         *
         * OPTIONAL
         */
        int (*read_proc) (struct seq_file *seq, struct scst_dev_type *dev_type);
        int (*write_proc) (char *buffer, char **start, off_t offset,
                int length, int *eof, struct scst_dev_type *dev_type);
#endif

        /*
         * Name of the dev handler. Must be unique. MUST HAVE.
         *
         * It's SCST_MAX_NAME + few more bytes to match scst_user expectations.
         */
        char name[SCST_MAX_NAME + 10];

        /*
         * Number of dedicated threads. If 0 - no dedicated threads will
         * be created, if <0 - creation of dedicated threads is prohibited.
         */
        int threads_num;

        /* Optional default log flags */
        const unsigned long default_trace_flags;

        /* Optional pointer to trace flags */
        unsigned long *trace_flags;

        /* Optional local trace table */
        struct scst_trace_log *trace_tbl;

        /* Optional local trace table help string */
        const char *trace_tbl_help;

#ifndef CONFIG_SCST_PROC
        /* Optional sysfs attributes */
        const struct attribute **devt_attrs;

        /* Optional sysfs device attributes */
        const struct attribute **dev_attrs;
#endif

        /* Pointer to dev handler's private data */
        void *devt_priv;

        /* Pointer to parent dev type in the sysfs hierarchy */
        struct scst_dev_type *parent;

        struct module *module;

        /** Private, must be inited to 0 by memset() **/

        /* list entry in scst_dev_type_list */
        struct list_head dev_type_list_entry;

#ifdef CONFIG_SCST_PROC
        /* The pointer to the /proc directory entry */
        struct proc_dir_entry *proc_dev_type_root;
#endif

        unsigned int devt_kobj_initialized:1;

        struct kobject devt_kobj; /* main handlers/driver */

        /* To wait until devt_kobj released */
        struct completion devt_kobj_release_compl;
};

struct scst_tgt {
        /* List of remote sessions per target, protected by scst_mutex */
        struct list_head sess_list;

        /* List entry of targets per template (tgts_list) */
        struct list_head tgt_list_entry;

        struct scst_tgt_template *tgtt; /* corresponding target template */

        struct scst_acg *default_acg; /* The default acg for this target. */

        /*
         * Maximum SG table size. Needed here, since different cards on the
         * same target template can have different SG table limitations.
         */
        int sg_tablesize;

        /* Used for storage of target driver private stuff */
        void *tgt_priv;

        /*
         * The following fields used to store and retry cmds if target's
         * internal queue is full, so the target is unable to accept
         * the cmd returning QUEUE FULL.
         * They protected by tgt_lock, where necessary.
         */
        bool retry_timer_active;
        struct timer_list retry_timer;
        atomic_t finished_cmds;
        int retry_cmds;
        spinlock_t tgt_lock;
        struct list_head retry_cmd_list;

        /* Used to wait until session finished to unregister */
        wait_queue_head_t unreg_waitQ;

#ifdef CONFIG_SCST_PROC
        /* Device number in /proc */
        int proc_num;
#endif

        /* Name of the target */
        char *tgt_name;

#ifdef CONFIG_SCST_PROC
        /* Name on the default security group ("Default_target_name") */
        char *default_group_name;
#endif

        /* Set if tgt_kobj was initialized */
        unsigned int tgt_kobj_initialized:1;

        struct kobject tgt_kobj; /* main targets/target kobject */
        struct kobject *tgt_sess_kobj; /* target/sessions/ */
        struct kobject *tgt_luns_kobj; /* target/luns/ */
        struct kobject *tgt_ini_grp_kobj; /* target/ini_groups/ */
};

/* Hash size and hash fn for hash based lun translation */
#define TGT_DEV_HASH_SHIFT      5
#define TGT_DEV_HASH_SIZE       (1 << TGT_DEV_HASH_SHIFT)
#define HASH_VAL(_val)          (_val & (TGT_DEV_HASH_SIZE - 1))

#ifdef CONFIG_SCST_MEASURE_LATENCY

/* Defines extended latency statistics */
struct scst_ext_latency_stat {
        uint64_t scst_time_rd, tgt_time_rd, dev_time_rd;
        unsigned int processed_cmds_rd;
        uint64_t min_scst_time_rd, min_tgt_time_rd, min_dev_time_rd;
        uint64_t max_scst_time_rd, max_tgt_time_rd, max_dev_time_rd;

        uint64_t scst_time_wr, tgt_time_wr, dev_time_wr;
        unsigned int processed_cmds_wr;
        uint64_t min_scst_time_wr, min_tgt_time_wr, min_dev_time_wr;
        uint64_t max_scst_time_wr, max_tgt_time_wr, max_dev_time_wr;
};

#define SCST_IO_SIZE_THRESHOLD_SMALL            (8*1024)
#define SCST_IO_SIZE_THRESHOLD_MEDIUM           (32*1024)
#define SCST_IO_SIZE_THRESHOLD_LARGE            (128*1024)
#define SCST_IO_SIZE_THRESHOLD_VERY_LARGE       (512*1024)

#define SCST_LATENCY_STAT_INDEX_SMALL           0
#define SCST_LATENCY_STAT_INDEX_MEDIUM          1
#define SCST_LATENCY_STAT_INDEX_LARGE           2
#define SCST_LATENCY_STAT_INDEX_VERY_LARGE      3
#define SCST_LATENCY_STAT_INDEX_OTHER           4
#define SCST_LATENCY_STATS_NUM          (SCST_LATENCY_STAT_INDEX_OTHER + 1)

#endif /* CONFIG_SCST_MEASURE_LATENCY */

struct scst_session {
        /*
         * Initialization phase, one of SCST_SESS_IPH_* constants, protected by
         * sess_list_lock
         */
        int init_phase;

        struct scst_tgt *tgt;   /* corresponding target */

        /* Used for storage of target driver private stuff */
        void *tgt_priv;

        unsigned long sess_aflags; /* session's async flags */

        /*
         * Hash list of tgt_dev's for this session, protected by scst_mutex
         * and suspended activity
         */
        struct list_head sess_tgt_dev_list_hash[TGT_DEV_HASH_SIZE];

        /*
         * List of cmds in this session. Used to find a cmd in the
         * session. Protected by sess_list_lock.
         */
        struct list_head search_cmd_list;

        spinlock_t sess_list_lock; /* protects search_cmd_list, etc */

        /*
         * List of cmds in this in the state after PRE_XMIT_RESP. All the cmds
         * moved here from search_cmd_list. Needed for hw_pending_work.
         * Protected by sess_list_lock.
         */
        struct list_head after_pre_xmit_cmd_list;

        atomic_t refcnt;                /* get/put counter */

        /*
         * Alive commands for this session. ToDo: make it part of the common
         * IO flow control.
         */
        atomic_t sess_cmd_count;

        /* Access control for this session and list entry there */
        struct scst_acg *acg;

        /* List entry for the sessions list inside ACG */
        struct list_head acg_sess_list_entry;

#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 20))
        struct delayed_work hw_pending_work;
#else
        struct work_struct hw_pending_work;
#endif

        /* Name of attached initiator */
        const char *initiator_name;

        /* List entry of sessions per target */
        struct list_head sess_list_entry;

        /* List entry for the list that keeps session, waiting for the init */
        struct list_head sess_init_list_entry;

        /*
         * List entry for the list that keeps session, waiting for the shutdown
         */
        struct list_head sess_shut_list_entry;

        /*
         * Lists of deferred during session initialization commands.
         * Protected by sess_list_lock.
         */
        struct list_head init_deferred_cmd_list;
        struct list_head init_deferred_mcmd_list;

        /*
         * Shutdown phase, one of SCST_SESS_SPH_* constants, unprotected.
         * Async. relating to init_phase, must be a separate variable, because
         * session could be unregistered before async. registration is finished.
         */
        unsigned long shut_phase;

        /* Used if scst_unregister_session() called in wait mode */
        struct completion *shutdown_compl;

        /* Set if sess_kobj was initialized */
        unsigned int sess_kobj_initialized:1;

        struct kobject sess_kobj; /* kobject for this struct */

        /*
         * Functions and data for user callbacks from scst_register_session()
         * and scst_unregister_session()
         */
        void *reg_sess_data;
        void (*init_result_fn) (struct scst_session *sess, void *data,
                                int result);
        void (*unreg_done_fn) (struct scst_session *sess);

#ifdef CONFIG_SCST_MEASURE_LATENCY
        /*
         * Must be the last to allow to work with drivers who don't know
         * about this config time option.
         */
        spinlock_t lat_lock;
        uint64_t scst_time, tgt_time, dev_time;
        unsigned int processed_cmds;
        uint64_t min_scst_time, min_tgt_time, min_dev_time;
        uint64_t max_scst_time, max_tgt_time, max_dev_time;
        struct scst_ext_latency_stat sess_latency_stat[SCST_LATENCY_STATS_NUM];
#endif
};

struct scst_cmd_lists {
        spinlock_t cmd_list_lock;
        struct list_head active_cmd_list;
        wait_queue_head_t cmd_list_waitQ;
        struct list_head lists_list_entry;
};

struct scst_cmd {
        /* List entry for below *_cmd_lists */
        struct list_head cmd_list_entry;

        /* Pointer to lists of commands with the lock */
        struct scst_cmd_lists *cmd_lists;

        atomic_t cmd_ref;

        struct scst_session *sess;      /* corresponding session */

        /* Cmd state, one of SCST_CMD_STATE_* constants */
        int state;

        /*************************************************************
         ** Cmd's flags
         *************************************************************/

        /*
         * Set if expected_sn should be incremented, i.e. cmd was sent
         * for execution
         */
        unsigned int sent_for_exec:1;

        /* Set if the cmd's action is completed */
        unsigned int completed:1;

        /* Set if we should ignore Unit Attention in scst_check_sense() */
        unsigned int ua_ignore:1;

        /* Set if cmd is being processed in atomic context */
        unsigned int atomic:1;

        /* Set if this command was sent in double UA possible state */
        unsigned int double_ua_possible:1;

        /* Set if this command contains status */
        unsigned int is_send_status:1;

        /* Set if cmd is being retried */
        unsigned int retry:1;

        /* Set if cmd is internally generated */
        unsigned int internal:1;

        /* Set if the device was blocked by scst_inc_on_dev_cmd() (for debug) */
        unsigned int inc_blocking:1;

        /* Set if the device should be unblocked after cmd's finish */
        unsigned int needs_unblocking:1;

        /* Set if scst_dec_on_dev_cmd() call is needed on the cmd's finish */
        unsigned int dec_on_dev_needed:1;

        /* Set if cmd is queued as hw pending */
        unsigned int cmd_hw_pending:1;

        /*
         * Set if the target driver wants to alloc data buffers on its own.
         * In this case alloc_data_buf() must be provided in the target driver
         * template.
         */
        unsigned int tgt_need_alloc_data_buf:1;

        /*
         * Set by SCST if the custom data buffer allocation by the target driver
         * succeeded.
         */
        unsigned int tgt_data_buf_alloced:1;

        /* Set if custom data buffer allocated by dev handler */
        unsigned int dh_data_buf_alloced:1;

        /* Set if the target driver called scst_set_expected() */
        unsigned int expected_values_set:1;

        /*
         * Set if the SG buffer was modified by scst_set_resp_data_len()
         */
        unsigned int sg_buff_modified:1;

        /*
         * Set if scst_cmd_init_stage1_done() called and the target
         * want that preprocessing_done() will be called
         */
        unsigned int preprocessing_only:1;

        /* Set if cmd's SN was set */
        unsigned int sn_set:1;

        /* Set if hq_cmd_count was incremented */
        unsigned int hq_cmd_inced:1;

        /*
         * Set if scst_cmd_init_stage1_done() called and the target wants
         * that the SN for the cmd won't be assigned until scst_restart_cmd()
         */
        unsigned int set_sn_on_restart_cmd:1;

        /* Set if the cmd's must not use sgv cache for data buffer */
        unsigned int no_sgv:1;

        /*
         * Set if target driver may need to call dma_sync_sg() or similar
         * function before transferring cmd' data to the target device
         * via DMA.
         */
        unsigned int may_need_dma_sync:1;

        /* Set if the cmd was done or aborted out of its SN */
        unsigned int out_of_sn:1;

        /* Set if increment expected_sn in cmd->scst_cmd_done() */
        unsigned int inc_expected_sn_on_done:1;

        /* Set if tgt_sn field is valid */
        unsigned int tgt_sn_set:1;

        /* Set if cmd is done */
        unsigned int done:1;

        /* Set if cmd is finished */
        unsigned int finished:1;

        /*
         * Set if the cmd was delayed by task management debugging code.
         * Used only if CONFIG_SCST_DEBUG_TM is on.
         */
        unsigned int tm_dbg_delayed:1;

        /*
         * Set if the cmd must be ignored by task management debugging code.
         * Used only if CONFIG_SCST_DEBUG_TM is on.
         */
        unsigned int tm_dbg_immut:1;

        /**************************************************************/

        unsigned long cmd_flags; /* cmd's async flags */

        /* Keeps status of cmd's status/data delivery to remote initiator */
        int delivery_status;

        struct scst_tgt_template *tgtt; /* to save extra dereferences */
        struct scst_tgt *tgt;           /* to save extra dereferences */
        struct scst_device *dev;        /* to save extra dereferences */

        struct scst_tgt_dev *tgt_dev;   /* corresponding device for this cmd */

        uint64_t lun;                   /* LUN for this cmd */

        unsigned long start_time;

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 18)
        struct scsi_request *scsi_req;  /* SCSI request */
#endif

        /* List entry for tgt_dev's SN related lists */
        struct list_head sn_cmd_list_entry;

        /* Cmd's serial number, used to execute cmd's in order of arrival */
        unsigned long sn;

        /* The corresponding sn_slot in tgt_dev->sn_slots */
        atomic_t *sn_slot;

        /* List entry for sess's search_cmd_list and after_pre_xmit_cmd_list */
        struct list_head sess_cmd_list_entry;

        /*
         * Used to found the cmd by scst_find_cmd_by_tag(). Set by the
         * target driver on the cmd's initialization time
         */
        uint64_t tag;

        uint32_t tgt_sn; /* SN set by target driver (for TM purposes) */

        /* CDB and its len */
        uint8_t cdb[SCST_MAX_CDB_SIZE];
        short cdb_len; /* it might be -1 */
        unsigned short ext_cdb_len;
        uint8_t *ext_cdb;

        enum scst_cdb_flags op_flags;
        const char *op_name;

        enum scst_cmd_queue_type queue_type;

        int timeout; /* CDB execution timeout in seconds */
        int retries; /* Amount of retries that will be done by SCSI mid-level */

        /* SCSI data direction, one of SCST_DATA_* constants */
        scst_data_direction data_direction;

        /* Remote initiator supplied values, if any */
        scst_data_direction expected_data_direction;
        int expected_transfer_len;
        int expected_in_transfer_len; /* for bidi writes */

        /*
         * Cmd data length. Could be different from bufflen for commands like
         * VERIFY, which transfer different amount of data (if any), than
         * processed.
         */
        int data_len;

        /* Completition routine */
        void (*scst_cmd_done) (struct scst_cmd *cmd, int next_state,
                enum scst_exec_context pref_context);

        struct sgv_pool_obj *sgv;       /* sgv object */
        int bufflen;                    /* cmd buffer length */
        struct scatterlist *sg;         /* cmd data buffer SG vector */
        int sg_cnt;                     /* SG segments count */

        /*
         * Response data length in data buffer. This field must not be set
         * directly, use scst_set_resp_data_len() for that
         */
        int resp_data_len;

        /* scst_get_sg_buf_[first,next]() support */
        int get_sg_buf_entry_num;

        /* Bidirectional transfers support */
        int in_bufflen;                 /* WRITE buffer length */
        struct sgv_pool_obj *in_sgv;    /* WRITE sgv object */
        struct scatterlist *in_sg;      /* WRITE data buffer SG vector */
        int in_sg_cnt;                  /* WRITE SG segments count */

        /*
         * Used if both target driver and dev handler request own memory
         * allocation. In other cases, both are equal to sg and sg_cnt
         * correspondingly.
         *
         * If target driver requests own memory allocations, it MUST use
         * functions scst_cmd_get_tgt_sg*() to get sg and sg_cnt! Otherwise,
         * it may use functions scst_cmd_get_sg*().
         */
        struct scatterlist *tgt_sg;
        int tgt_sg_cnt;
        struct scatterlist *tgt_in_sg;  /* bidirectional */
        int tgt_in_sg_cnt;              /* bidirectional */

        /*
         * The status fields in case of errors must be set using
         * scst_set_cmd_error_status()!
         */
        uint8_t status;         /* status byte from target device */
        uint8_t msg_status;     /* return status from host adapter itself */
        uint8_t host_status;    /* set by low-level driver to indicate status */
        uint8_t driver_status;  /* set by mid-level */

        uint8_t *sense;         /* pointer to sense buffer */
        unsigned short sense_valid_len; /* length of valid sense data */
        unsigned short sense_buflen; /* length of the sense buffer, if any */

        /* Start time when cmd was sent to rdy_to_xfer() or xmit_response() */
        unsigned long hw_pending_start;

        /* Used for storage of target driver private stuff */
        void *tgt_priv;

        /* Used for storage of dev handler private stuff */
        void *dh_priv;

        /*
         * Used to restore the SG vector if it was modified by
         * scst_set_resp_data_len()
         */
        int orig_sg_cnt, orig_sg_entry, orig_entry_len;

        /* Used to retry commands in case of double UA */
        int dbl_ua_orig_resp_data_len, dbl_ua_orig_data_direction;

        /* List corresponding mgmt cmd, if any, protected by sess_list_lock */
        struct list_head mgmt_cmd_list;

        /* List entry for dev's blocked_cmd_list */
        struct list_head blocked_cmd_list_entry;

        struct scst_cmd *orig_cmd; /* Used to issue REQUEST SENSE */

#ifdef CONFIG_SCST_MEASURE_LATENCY
        /*
         * Must be the last to allow to work with drivers who don't know
         * about this config time option.
         */
        uint64_t start, curr_start, parse_time, alloc_buf_time;
        uint64_t restart_waiting_time, rdy_to_xfer_time;
        uint64_t pre_exec_time, exec_time, dev_done_time;
        uint64_t xmit_time, tgt_on_free_time, dev_on_free_time;
#endif
};

struct scst_rx_mgmt_params {
        int fn;
        uint64_t tag;
        const uint8_t *lun;
        int lun_len;
        uint32_t cmd_sn;
        int atomic;
        void *tgt_priv;
        unsigned char tag_set;
        unsigned char lun_set;
        unsigned char cmd_sn_set;
};

struct scst_mgmt_cmd_stub {
        struct scst_mgmt_cmd *mcmd;

        /* List entry in cmd->mgmt_cmd_list */
        struct list_head cmd_mgmt_cmd_list_entry;
};

struct scst_mgmt_cmd {
        /* List entry for *_mgmt_cmd_list */
        struct list_head mgmt_cmd_list_entry;

        struct scst_session *sess;

        /* Mgmt cmd state, one of SCST_MCMD_STATE_* constants */
        int state;

        int fn;

        unsigned int completed:1;       /* set, if the mcmd is completed */
        /* Set if device(s) should be unblocked after mcmd's finish */
        unsigned int needs_unblocking:1;
        unsigned int lun_set:1;         /* set, if lun field is valid */
        unsigned int cmd_sn_set:1;      /* set, if cmd_sn field is valid */
        /* set, if scst_mgmt_affected_cmds_done was called */
        unsigned int affected_cmds_done_called:1;

        /*
         * Number of commands to finish before sending response,
         * protected by scst_mcmd_lock
         */
        int cmd_finish_wait_count;

        /*
         * Number of commands to complete (done) before resetting reservation,
         * protected by scst_mcmd_lock
         */
        int cmd_done_wait_count;

        /* Number of completed commands, protected by scst_mcmd_lock */
        int completed_cmd_count;

        uint64_t lun;   /* LUN for this mgmt cmd */
        /* or (and for iSCSI) */
        uint64_t tag;   /* tag of the corresponding cmd */

        uint32_t cmd_sn; /* affected command's highest SN */

        /* corresponding cmd (to be aborted, found by tag) */
        struct scst_cmd *cmd_to_abort;

        /* corresponding device for this mgmt cmd (found by lun) */
        struct scst_tgt_dev *mcmd_tgt_dev;

        /* completition status, one of the SCST_MGMT_STATUS_* constants */
        int status;

        /* Used for storage of target driver private stuff */
        void *tgt_priv;
};

struct scst_device {
        struct scst_dev_type *handler;  /* corresponding dev handler */

        struct scst_mem_lim dev_mem_lim;

        unsigned short type;    /* SCSI type of the device */

        /*************************************************************
         ** Dev's flags. Updates serialized by dev_lock or suspended
         ** activity
         *************************************************************/

        /* Set if dev is RESERVED */
        unsigned short dev_reserved:1;

        /* Set if double reset UA is possible */
        unsigned short dev_double_ua_possible:1;

        /* If set, dev is read only */
        unsigned short rd_only:1;

        /**************************************************************/

        /*************************************************************
         ** Dev's control mode page related values. Updates serialized
         ** by scst_block_dev(). It's long to not interfere with the
         ** above flags.
         *************************************************************/

        unsigned long queue_alg:4;
        unsigned long tst:3;
        unsigned long tas:1;
        unsigned long swp:1;
        unsigned long d_sense:1;

        /*
         * Set if device implements own ordered commands management. If not set
         * and queue_alg is SCST_CONTR_MODE_QUEUE_ALG_RESTRICTED_REORDER,
         * expected_sn will be incremented only after commands finished.
         */
        unsigned long has_own_order_mgmt:1;

        /**************************************************************/

        /* Used for storage of dev handler private stuff */
        void *dh_priv;

        /* Used to translate SCSI's cmd to SCST's cmd */
        struct gendisk *rq_disk;

        /* Corresponding real SCSI device, could be NULL for virtual devices */
        struct scsi_device *scsi_dev;

        /* Pointer to lists of commands with the lock */
        struct scst_cmd_lists *p_cmd_lists;

        /* Lists of commands with lock, if dedicated threads are used */
        struct scst_cmd_lists cmd_lists;

        /* Per-device dedicated IO context */
        struct io_context *dev_io_ctx;

        /* How many cmds alive on this dev */
        atomic_t dev_cmd_count;

        /* How many write cmds alive on this dev. Temporary, ToDo */
        atomic_t write_cmd_count;

        spinlock_t dev_lock;            /* device lock */

        /*
         * How many times device was blocked for new cmds execution.
         * Protected by dev_lock
         */
        int block_count;

        /*
         * How many there are "on_dev" commands, i.e. ones those are being
         * executed by the underlying SCSI/virtual device.
         */
        atomic_t on_dev_count;

        struct list_head blocked_cmd_list; /* protected by dev_lock */

        /* Used to wait for requested amount of "on_dev" commands */
        wait_queue_head_t on_dev_waitQ;

        /* A list entry used during TM, protected by scst_mutex */
        struct list_head tm_dev_list_entry;

        /* Virtual device internal ID */
        int virt_id;

        /* Pointer to virtual device name, for convenience only */
        char *virt_name;

        /* List entry in global devices list */
        struct list_head dev_list_entry;

        /*
         * List of tgt_dev's, one per session, protected by scst_mutex or
         * dev_lock for reads and both for writes
         */
        struct list_head dev_tgt_dev_list;

        /* List of acg_dev's, one per acg, protected by scst_mutex */
        struct list_head dev_acg_dev_list;

        /* List of dedicated threads, protected by scst_mutex */
        struct list_head threads_list;

        /* Device number */
        int dev_num;

        /* Set if tgt_kobj was initialized */
        unsigned int dev_kobj_initialized:1;

        struct kobject dev_kobj; /* kobject for this struct */
        struct kobject *dev_exp_kobj; /* exported groups */

        /* Export number in the dev's sysfs list. Protected by scst_mutex */
        int dev_exported_lun_num;
};

/*
 * Used to store threads local tgt_dev specific data
 */
struct scst_thr_data_hdr {
        /* List entry in tgt_dev->thr_data_list */
        struct list_head thr_data_list_entry;
        struct task_struct *owner_thr; /* the owner thread */
        atomic_t ref;
        /* Function that will be called on the tgt_dev destruction */
        void (*free_fn) (struct scst_thr_data_hdr *data);
};

/*
 * Used to store per-session specific device information
 */
struct scst_tgt_dev {
        /* List entry in sess->sess_tgt_dev_list_hash */
        struct list_head sess_tgt_dev_list_entry;

        struct scst_device *dev; /* to save extra dereferences */
        uint64_t lun;            /* to save extra dereferences */

        gfp_t gfp_mask;
        struct sgv_pool *pool;
        int max_sg_cnt;

        unsigned long tgt_dev_flags;    /* tgt_dev's async flags */

        /* Used for storage of dev handler private stuff */
        void *dh_priv;

        /* How many cmds alive on this dev in this session */
        atomic_t tgt_dev_cmd_count;

        /*
         * Used to execute cmd's in order of arrival, honoring SCSI task
         * attributes.
         *
         * Protected by sn_lock, except expected_sn, which is protected by
         * itself. Curr_sn must have the same size as expected_sn to
         * overflow simultaneously.
         */
        int def_cmd_count;
        spinlock_t sn_lock;
        unsigned long expected_sn;
        unsigned long curr_sn;
        int hq_cmd_count;
        struct list_head deferred_cmd_list;
        struct list_head skipped_sn_list;

        /*
         * Set if the prev cmd was ORDERED. Size must allow unprotected
         * modifications independant to the neighbour fields.
         */
        unsigned long prev_cmd_ordered;

        int num_free_sn_slots; /* if it's <0, then all slots are busy */
        atomic_t *cur_sn_slot;
        atomic_t sn_slots[15];

        /* List of scst_thr_data_hdr and lock */
        spinlock_t thr_data_lock;
        struct list_head thr_data_list;

        /* Per-(device, session) dedicated IO context */
        struct io_context *tgt_dev_io_ctx;

        spinlock_t tgt_dev_lock;        /* per-session device lock */

        /* List of UA's for this device, protected by tgt_dev_lock */
        struct list_head UA_list;

        struct scst_session *sess;      /* corresponding session */
        struct scst_acg_dev *acg_dev;   /* corresponding acg_dev */

        /* List entry in dev->dev_tgt_dev_list */
        struct list_head dev_tgt_dev_list_entry;

        /* Internal tmp list entry */
        struct list_head extra_tgt_dev_list_entry;

        /* Set if INQUIRY DATA HAS CHANGED UA is needed */
        unsigned int inq_changed_ua_needed:1;

        /*
         * Stored Unit Attention sense and its length for possible
         * subsequent REQUEST SENSE. Both protected by tgt_dev_lock.
         */
        unsigned short tgt_dev_valid_sense_len;
        uint8_t tgt_dev_sense[SCST_SENSE_BUFFERSIZE];

#ifdef CONFIG_SCST_MEASURE_LATENCY
        /*
         * Must be the last to allow to work with drivers who don't know
         * about this config time option.
         *
         * Protected by sess->lat_lock.
         */
        uint64_t scst_time, tgt_time, dev_time;
        unsigned int processed_cmds;
        struct scst_ext_latency_stat dev_latency_stat[SCST_LATENCY_STATS_NUM];
#endif
};

/*
 * Used to store ACG-specific device information, like LUN
 */
struct scst_acg_dev {
        struct scst_device *dev; /* corresponding device */

        uint64_t lun; /* device's LUN in this acg */

        /* If set, the corresponding LU is read only */
        unsigned int rd_only:1;

        /* Set if acg_dev_kobj was initialized */
        unsigned int acg_dev_kobj_initialized:1;

        struct scst_acg *acg; /* parent acg */

        /* List entry in dev->dev_acg_dev_list */
        struct list_head dev_acg_dev_list_entry;

        /* List entry in acg->acg_dev_list */
        struct list_head acg_dev_list_entry;

        /* kobject for this structure */
        struct kobject acg_dev_kobj;
};

/*
 * ACG - access control group. Used to store group related
 * control information.
 */
struct scst_acg {
        /* List of acg_dev's in this acg, protected by scst_mutex */
        struct list_head acg_dev_list;

        /* List of attached sessions, protected by scst_mutex */
        struct list_head acg_sess_list;

        /* List of attached acn's, protected by scst_mutex */
        struct list_head acn_list;

        /* List entry in scst_acg_list */
        struct list_head scst_acg_list_entry;

        /* Name of this acg */
        const char *acg_name;

#ifdef CONFIG_SCST_PROC
        /* The pointer to the /proc directory entry */
        struct proc_dir_entry *acg_proc_root;
#endif
};

/*
 * ACN - access control name. Used to store names, by which
 * incoming sessions will be assigned to appropriate ACG.
 */
struct scst_acn {
        /* Initiator's name */
        const char *name;
        /* List entry in acg->acn_list */
        struct list_head acn_list_entry;
};

/*
 * Used to store per-session UNIT ATTENTIONs
 */
struct scst_tgt_dev_UA {
        /* List entry in tgt_dev->UA_list */
        struct list_head UA_list_entry;

        /* Set if UA is global for session */
        unsigned short global_UA:1;

        /* Unit Attention valid sense len */
        unsigned short UA_valid_sense_len;
        /* Unit Attention sense buf */
        uint8_t UA_sense_buffer[SCST_SENSE_BUFFERSIZE];
};

/* Used to deliver AENs */
struct scst_aen {
        int event_fn; /* AEN fn */

        struct scst_session *sess;      /* corresponding session */
        uint64_t lun;                   /* corresponding LUN in SCSI form */

        union {
                /* SCSI AEN data */
                struct {
                        int aen_sense_len;
                        uint8_t aen_sense[SCST_STANDARD_SENSE_LEN];
                };
        };

        /* Keeps status of AEN's delivery to remote initiator */
        int delivery_status;
};

#ifndef smp_mb__after_set_bit
/* There is no smp_mb__after_set_bit() in the kernel */
#define smp_mb__after_set_bit()                 smp_mb()
#endif

/*
 * Registers target template
 * Returns 0 on success or appropriate error code otherwise
 */
int __scst_register_target_template(struct scst_tgt_template *vtt,
        const char *version);
static inline int scst_register_target_template(struct scst_tgt_template *vtt)
{
        return __scst_register_target_template(vtt, SCST_INTERFACE_VERSION);
}

/*
 * Unregisters target template
 */
void scst_unregister_target_template(struct scst_tgt_template *vtt);

/*
 * Registers and returns target adapter
 * Returns new target structure on success or NULL otherwise.
 *
 * If parameter "target_name" isn't NULL, then security group with name
 * "Default_##target_name", if created, will be used as the default
 * instead of "Default" one for all initiators not assigned to any other group.
 */
struct scst_tgt *scst_register(struct scst_tgt_template *vtt,
        const char *target_name);

/*
 * Unregisters target adapter
 */
void scst_unregister(struct scst_tgt *tgt);

/*
 * Registers and returns a session
 *
 * Returns new session on success or NULL otherwise
 *
 * Parameters:
 *   tgt    - target
 *   atomic - true, if the function called in the atomic context. If false,
 *      this function will block until the session registration is completed.
 *   initiator_name - remote initiator's name, any NULL-terminated string,
 *      e.g. iSCSI name, which used as the key to found appropriate access
 *      control group. Could be NULL, then the default target's LUNs are used.
 *   data - any target driver supplied data
 *   result_fn - pointer to the function that will be
 *      asynchronously called when session initialization finishes.
 *      Can be NULL. Parameters:
 *       - sess - session
 *       - data - target driver supplied to scst_register_session() data
 *       - result - session initialization result, 0 on success or
 *                  appropriate error code otherwise
 *
 * Note: A session creation and initialization is a complex task,
 *       which requires sleeping state, so it can't be fully done
 *       in interrupt context. Therefore the "bottom half" of it, if
 *       scst_register_session() is called from atomic context, will be
 *       done in SCST thread context. In this case scst_register_session()
 *       will return not completely initialized session, but the target
 *       driver can supply commands to this session via scst_rx_cmd().
 *       Those commands processing will be delayed inside SCST until
 *       the session initialization is finished, then their processing
 *       will be restarted. The target driver will be notified about
 *       finish of the session initialization by function result_fn().
 *       On success the target driver could do nothing, but if the
 *       initialization fails, the target driver must ensure that
 *       no more new commands being sent or will be sent to SCST after
 *       result_fn() returns. All already sent to SCST commands for
 *       failed session will be returned in xmit_response() with BUSY status.
 *       In case of failure the driver shall call scst_unregister_session()
 *       inside result_fn(), it will NOT be called automatically.
 */
struct scst_session *scst_register_session(struct scst_tgt *tgt, int atomic,
        const char *initiator_name, void *data,
        void (*result_fn) (struct scst_session *sess, void *data, int result));

/*
 * Unregisters a session.
 * Parameters:
 *   sess - session to be unregistered
 *   wait - if true, instructs to wait until all commands, which
 *      currently is being executed and belonged to the session, finished.
 *      Otherwise, target driver should be prepared to receive
 *      xmit_response() for the session's command after
 *      scst_unregister_session() returns.
 *   unreg_done_fn - pointer to the function that will be
 *      asynchronously called when the last session's command finishes and
 *      the session is about to be completely freed. Can be NULL.
 *      Parameter:
 *       - sess - session
 *
 * Notes:
 *
 * - All outstanding commands will be finished regularly. After
 *   scst_unregister_session() returned no new commands must be sent to
 *   SCST via scst_rx_cmd().
 *
 * - The caller must ensure that no scst_rx_cmd() or scst_rx_mgmt_fn_*() is
 *   called in paralell with scst_unregister_session().
 *
 * - Can be called before result_fn() of scst_register_session() called,
 *   i.e. during the session registration/initialization.
 *
 * - It is highly recommended to call scst_unregister_session() as soon as it
 *   gets clear that session will be unregistered and not to wait until all
 *   related commands finished. This function provides the wait functionality,
 *   but it also starts recovering stuck commands, if there are any.
 *   Otherwise, your target driver could wait for those commands forever.
 */
void scst_unregister_session(struct scst_session *sess, int wait,
        void (*unreg_done_fn) (struct scst_session *sess));

/*
 * Registers dev handler driver
 * Returns 0 on success or appropriate error code otherwise
 */
int __scst_register_dev_driver(struct scst_dev_type *dev_type,
        const char *version);
static inline int scst_register_dev_driver(struct scst_dev_type *dev_type)
{
        return __scst_register_dev_driver(dev_type, SCST_INTERFACE_VERSION);
}

/*
 * Unregisters dev handler driver
 */
void scst_unregister_dev_driver(struct scst_dev_type *dev_type);

/*
 * Registers dev handler driver for virtual devices (eg VDISK)
 * Returns 0 on success or appropriate error code otherwise
 */
int __scst_register_virtual_dev_driver(struct scst_dev_type *dev_type,
        const char *version);
static inline int scst_register_virtual_dev_driver(
        struct scst_dev_type *dev_type)
{
        return __scst_register_virtual_dev_driver(dev_type,
                SCST_INTERFACE_VERSION);
}

/*
 * Unregisters dev handler driver for virtual devices
 */
void scst_unregister_virtual_dev_driver(struct scst_dev_type *dev_type);

/*
 * Creates and sends new command to SCST.
 * Must not be called in parallel with scst_unregister_session() for the
 * same sess. Returns the command on success or NULL otherwise
 */
struct scst_cmd *scst_rx_cmd(struct scst_session *sess,
        const uint8_t *lun, int lun_len, const uint8_t *cdb,
        int cdb_len, int atomic);

/*
 * Notifies SCST that the driver finished its part of the command
 * initialization, and the command is ready for execution.
 * The second argument sets preferred command execition context.
 * See SCST_CONTEXT_* constants for details.
 *
 * !!IMPORTANT!!
 *
 * If cmd->set_sn_on_restart_cmd not set, this function, as well as
 * scst_cmd_init_stage1_done() and scst_restart_cmd(), must not be
 * called simultaneously for the same session (more precisely,
 * for the same session/LUN, i.e. tgt_dev), i.e. they must be
 * somehow externally serialized. This is needed to have lock free fast path in
 * scst_cmd_set_sn(). For majority of targets those functions are naturally
 * serialized by the single source of commands. Only iSCSI immediate commands
 * with multiple connections per session seems to be an exception. For it, some
 * mutex/lock shall be used for the serialization.
 */
void scst_cmd_init_done(struct scst_cmd *cmd,
        enum scst_exec_context pref_context);

/*
 * Notifies SCST that the driver finished the first stage of the command
 * initialization, and the command is ready for execution, but after
 * SCST done the command's preprocessing preprocessing_done() function
 * should be called. The second argument sets preferred command execition
 * context. See SCST_CONTEXT_* constants for details.
 *
 * See also scst_cmd_init_done() comment for the serialization requirements.
 */
static inline void scst_cmd_init_stage1_done(struct scst_cmd *cmd,
        enum scst_exec_context pref_context, int set_sn)
{
        cmd->preprocessing_only = 1;
        cmd->set_sn_on_restart_cmd = !set_sn;
        scst_cmd_init_done(cmd, pref_context);
}

/*
 * Notifies SCST that the driver finished its part of the command's
 * preprocessing and it is ready for further processing.
 * The second argument sets data receiving completion status
 * (see SCST_PREPROCESS_STATUS_* constants for details)
 * The third argument sets preferred command execition context
 * (see SCST_CONTEXT_* constants for details).
 *
 * See also scst_cmd_init_done() comment for the serialization requirements.
 */
void scst_restart_cmd(struct scst_cmd *cmd, int status,
        enum scst_exec_context pref_context);

/*
 * Notifies SCST that the driver received all the necessary data
 * and the command is ready for further processing.
 * The second argument sets data receiving completion status
 * (see SCST_RX_STATUS_* constants for details)
 * The third argument sets preferred command execition context
 * (see SCST_CONTEXT_* constants for details)
 */
void scst_rx_data(struct scst_cmd *cmd, int status,
        enum scst_exec_context pref_context);

/*
 * Notifies SCST that the driver sent the response and the command
 * can be freed now. Don't forget to set the delivery status, if it
 * isn't success, using scst_set_delivery_status() before calling
 * this function. The third argument sets preferred command execition
 * context (see SCST_CONTEXT_* constants for details)
 */
void scst_tgt_cmd_done(struct scst_cmd *cmd,
        enum scst_exec_context pref_context);

/*
 * Creates new management command sends it for execution.
 * Must not be called in parallel with scst_unregister_session() for the
 * same sess. Returns 0 for success, error code otherwise.
 */
int scst_rx_mgmt_fn(struct scst_session *sess,
        const struct scst_rx_mgmt_params *params);

/*
 * Creates new management command using tag and sends it for execution.
 * Can be used for SCST_ABORT_TASK only.
 * Must not be called in parallel with scst_unregister_session() for the
 * same sess. Returns 0 for success, error code otherwise.
 *
 * Obsolete in favor of scst_rx_mgmt_fn()
 */
static inline int scst_rx_mgmt_fn_tag(struct scst_session *sess, int fn,
        uint64_t tag, int atomic, void *tgt_priv)
{
        struct scst_rx_mgmt_params params;

        BUG_ON(fn != SCST_ABORT_TASK);

        memset(&params, 0, sizeof(params));
        params.fn = fn;
        params.tag = tag;
        params.tag_set = 1;
        params.atomic = atomic;
        params.tgt_priv = tgt_priv;
        return scst_rx_mgmt_fn(sess, &params);
}

/*
 * Creates new management command using LUN and sends it for execution.
 * Currently can be used for any fn, except SCST_ABORT_TASK.
 * Must not be called in parallel with scst_unregister_session() for the
 * same sess. Returns 0 for success, error code otherwise.
 *
 * Obsolete in favor of scst_rx_mgmt_fn()
 */
static inline int scst_rx_mgmt_fn_lun(struct scst_session *sess, int fn,
        const uint8_t *lun, int lun_len, int atomic, void *tgt_priv)
{
        struct scst_rx_mgmt_params params;

        BUG_ON(fn == SCST_ABORT_TASK);

        memset(&params, 0, sizeof(params));
        params.fn = fn;
        params.lun = lun;
        params.lun_len = lun_len;
        params.lun_set = 1;
        params.atomic = atomic;
        params.tgt_priv = tgt_priv;
        return scst_rx_mgmt_fn(sess, &params);
}

/*
 * Provides various info about command's CDB.
 *
 * Returns: 0 on success, <0 if command is unknown, >0 if command is invalid.
 */
int scst_get_cdb_info(struct scst_cmd *cmd);

/*
 * Set error SCSI status in the command and prepares it for returning it
 */
void scst_set_cmd_error_status(struct scst_cmd *cmd, int status);

/*
 * Set error in the command and fill the sense buffer
 */
void scst_set_cmd_error(struct scst_cmd *cmd, int key, int asc, int ascq);

/*
 * Sets BUSY or TASK QUEUE FULL status
 */
void scst_set_busy(struct scst_cmd *cmd);

/*
 * Check if sense in the sense buffer, if any, in the correct format. If not,
 * convert it to the correct format.
 */
void scst_check_convert_sense(struct scst_cmd *cmd);

/*
 * Sets initial Unit Attention for sess, replacing default scst_sense_reset_UA
 */
void scst_set_initial_UA(struct scst_session *sess, int key, int asc, int ascq);

/*
 * Notifies SCST core that dev changed its capacity
 */
void scst_capacity_data_changed(struct scst_device *dev);

/*
 * Finds a command based on the supplied tag comparing it with one
 * that previously set by scst_cmd_set_tag().
 * Returns the command on success or NULL otherwise
 */
struct scst_cmd *scst_find_cmd_by_tag(struct scst_session *sess, uint64_t tag);

/*
 * Finds a command based on user supplied data and comparision
 * callback function, that should return true, if the command is found.
 * Returns the command on success or NULL otherwise
 */
struct scst_cmd *scst_find_cmd(struct scst_session *sess, void *data,
                               int (*cmp_fn) (struct scst_cmd *cmd,
                                              void *data));

/*
 * Translates SCST's data direction to DMA one from backend storage
 * perspective.
 */
enum dma_data_direction scst_to_dma_dir(int scst_dir);

/*
 * Translates SCST data direction to DMA data direction from the perspective
 * of the target device.
 */
enum dma_data_direction scst_to_tgt_dma_dir(int scst_dir);

/*
 * Returns true, if cmd's CDB is locally handled by SCST and 0 otherwise.
 * Dev handlers parse() and dev_done() not called for such commands.
 */
static inline bool scst_is_cmd_local(struct scst_cmd *cmd)
{
        return (cmd->op_flags & SCST_LOCAL_CMD) != 0;
}

/* Returns true, if cmd can deliver UA */
static inline bool scst_is_ua_command(struct scst_cmd *cmd)
{
        return (cmd->op_flags & SCST_SKIP_UA) == 0;
}

/*
 * Registers a virtual device.
 * Parameters:
 *   dev_type - the device's device handler
 *   dev_name - the new device name, NULL-terminated string. Must be uniq
 *              among all virtual devices in the system. The value isn't
 *              copied, only the reference is stored, so the value must
 *              remain valid during the device lifetime.
 * Returns assinged to the device ID on success, or negative value otherwise
 */
int scst_register_virtual_device(struct scst_dev_type *dev_handler,
        const char *dev_name);

/*
 * Unegisters a virtual device.
 * Parameters:
 *   id - the device's ID, returned by the registration function
 */
void scst_unregister_virtual_device(int id);

/*
 * Get/Set functions for tgt's sg_tablesize
 */
static inline int scst_tgt_get_sg_tablesize(struct scst_tgt *tgt)
{
        return tgt->sg_tablesize;
}

static inline void scst_tgt_set_sg_tablesize(struct scst_tgt *tgt, int val)
{
        tgt->sg_tablesize = val;
}

/*
 * Get/Set functions for tgt's target private data
 */
static inline void *scst_tgt_get_tgt_priv(struct scst_tgt *tgt)
{
        return tgt->tgt_priv;
}

static inline void scst_tgt_set_tgt_priv(struct scst_tgt *tgt, void *val)
{
        tgt->tgt_priv = val;
}

/*
 * Get/Set functions for session's target private data
 */
static inline void *scst_sess_get_tgt_priv(struct scst_session *sess)
{
        return sess->tgt_priv;
}

static inline void scst_sess_set_tgt_priv(struct scst_session *sess,
                                              void *val)
{
        sess->tgt_priv = val;
}

/**
 * Returns TRUE if cmd is being executed in atomic context.
 *
 * Note: checkpatch will complain on the use of in_atomic() below. You can
 * safely ignore this warning since in_atomic() is used here only for debugging
 * purposes.
 */
static inline int scst_cmd_atomic(struct scst_cmd *cmd)
{
        int res = cmd->atomic;
#ifdef CONFIG_SCST_EXTRACHECKS
        if (unlikely((in_atomic() || in_interrupt() || irqs_disabled()) &&
                     !res)) {
                printk(KERN_ERR "ERROR: atomic context and non-atomic cmd\n");
                dump_stack();
                cmd->atomic = 1;
                res = 1;
        }
#endif
        return res;
}

static inline enum scst_exec_context __scst_estimate_context(bool direct)
{
        if (in_irq())
                return SCST_CONTEXT_TASKLET;
        else if (irqs_disabled())
                return SCST_CONTEXT_THREAD;
        else
                return direct ? SCST_CONTEXT_DIRECT :
                                SCST_CONTEXT_DIRECT_ATOMIC;
}

static inline enum scst_exec_context scst_estimate_context(void)
{
        return __scst_estimate_context(0);
}

static inline enum scst_exec_context scst_estimate_context_direct(void)
{
        return __scst_estimate_context(1);
}

/* Returns cmd's CDB */
static inline const uint8_t *scst_cmd_get_cdb(struct scst_cmd *cmd)
{
        return cmd->cdb;
}

/* Returns cmd's CDB length */
static inline int scst_cmd_get_cdb_len(struct scst_cmd *cmd)
{
        return cmd->cdb_len;
}

/* Returns cmd's extended CDB */
static inline const uint8_t *scst_cmd_get_ext_cdb(struct scst_cmd *cmd)
{
        return cmd->ext_cdb;
}

/* Returns cmd's extended CDB length */
static inline int scst_cmd_get_ext_cdb_len(struct scst_cmd *cmd)
{
        return cmd->ext_cdb_len;
}

/* Sets cmd's extended CDB and its length */
static inline void scst_cmd_set_ext_cdb(struct scst_cmd *cmd,
        uint8_t *ext_cdb, unsigned int ext_cdb_len)
{
        cmd->ext_cdb = ext_cdb;
        cmd->ext_cdb_len = ext_cdb_len;
}

/* Returns cmd's session */
static inline struct scst_session *scst_cmd_get_session(struct scst_cmd *cmd)
{
        return cmd->sess;
}

/* Returns cmd's response data length */
static inline int scst_cmd_get_resp_data_len(struct scst_cmd *cmd)
{
        return cmd->resp_data_len;
}

/* Returns if status should be sent for cmd */
static inline int scst_cmd_get_is_send_status(struct scst_cmd *cmd)
{
        return cmd->is_send_status;
}

/*
 * Returns pointer to cmd's SG data buffer.
 *
 * Usage of this function is not recommended, use scst_get_buf_*()
 * family of functions instead.
 */
static inline struct scatterlist *scst_cmd_get_sg(struct scst_cmd *cmd)
{
        return cmd->sg;
}

/*
 * Returns cmd's sg_cnt.
 *
 * Usage of this function is not recommended, use scst_get_buf_*()
 * family of functions instead.
 */
static inline int scst_cmd_get_sg_cnt(struct scst_cmd *cmd)
{
        return cmd->sg_cnt;
}

/*
 * Returns cmd's data buffer length.
 *
 * In case if you need to iterate over data in the buffer, usage of
 * this function is not recommended, use scst_get_buf_*()
 * family of functions instead.
 */
static inline unsigned int scst_cmd_get_bufflen(struct scst_cmd *cmd)
{
        return cmd->bufflen;
}

/*
 * Returns pointer to cmd's bidirectional in (WRITE) SG data buffer.
 *
 * Usage of this function is not recommended, use scst_get_in_buf_*()
 * family of functions instead.
 */
static inline struct scatterlist *scst_cmd_get_in_sg(struct scst_cmd *cmd)
{
        return cmd->in_sg;
}

/*
 * Returns cmd's bidirectional in (WRITE) sg_cnt.
 *
 * Usage of this function is not recommended, use scst_get_in_buf_*()
 * family of functions instead.
 */
static inline int scst_cmd_get_in_sg_cnt(struct scst_cmd *cmd)
{
        return cmd->in_sg_cnt;
}

/*
 * Returns cmd's bidirectional in (WRITE) data buffer length.
 *
 * In case if you need to iterate over data in the buffer, usage of
 * this function is not recommended, use scst_get_in_buf_*()
 * family of functions instead.
 */
static inline unsigned int scst_cmd_get_in_bufflen(struct scst_cmd *cmd)
{
        return cmd->in_bufflen;
}

/* Returns pointer to cmd's target's SG data buffer */
static inline struct scatterlist *scst_cmd_get_tgt_sg(struct scst_cmd *cmd)
{
        return cmd->tgt_sg;
}

/* Returns cmd's target's sg_cnt */
static inline int scst_cmd_get_tgt_sg_cnt(struct scst_cmd *cmd)
{
        return cmd->tgt_sg_cnt;
}

/* Sets cmd's target's SG data buffer */
static inline void scst_cmd_set_tgt_sg(struct scst_cmd *cmd,
        struct scatterlist *sg, int sg_cnt)
{
        cmd->tgt_sg = sg;
        cmd->tgt_sg_cnt = sg_cnt;
        cmd->tgt_data_buf_alloced = 1;
}

/* Returns pointer to cmd's target's IN SG data buffer */
static inline struct scatterlist *scst_cmd_get_in_tgt_sg(struct scst_cmd *cmd)
{
        return cmd->tgt_in_sg;
}

/* Returns cmd's target's IN sg_cnt */
static inline int scst_cmd_get_tgt_in_sg_cnt(struct scst_cmd *cmd)
{
        return cmd->tgt_in_sg_cnt;
}

/* Sets cmd's target's IN SG data buffer */
static inline void scst_cmd_set_tgt_in_sg(struct scst_cmd *cmd,
        struct scatterlist *sg, int sg_cnt)
{
        WARN_ON(!cmd->tgt_data_buf_alloced);

        cmd->tgt_in_sg = sg;
        cmd->tgt_in_sg_cnt = sg_cnt;
}

/* Returns cmd's data direction */
static inline scst_data_direction scst_cmd_get_data_direction(
        struct scst_cmd *cmd)
{
        return cmd->data_direction;
}

/* Returns cmd's status byte from host device */
static inline uint8_t scst_cmd_get_status(struct scst_cmd *cmd)
{
        return cmd->status;
}

/* Returns cmd's status from host adapter itself */
static inline uint8_t scst_cmd_get_msg_status(struct scst_cmd *cmd)
{
        return cmd->msg_status;
}

/* Returns cmd's status set by low-level driver to indicate its status */
static inline uint8_t scst_cmd_get_host_status(struct scst_cmd *cmd)
{
        return cmd->host_status;
}

/* Returns cmd's status set by SCSI mid-level */
static inline uint8_t scst_cmd_get_driver_status(struct scst_cmd *cmd)
{
        return cmd->driver_status;
}

/* Returns pointer to cmd's sense buffer */
static inline uint8_t *scst_cmd_get_sense_buffer(struct scst_cmd *cmd)
{
        return cmd->sense;
}

/* Returns cmd's valid sense length */
static inline int scst_cmd_get_sense_buffer_len(struct scst_cmd *cmd)
{
        return cmd->sense_valid_len;
}

/*
 * Get/Set functions for cmd's target SN
 */
static inline uint64_t scst_cmd_get_tag(struct scst_cmd *cmd)
{
        return cmd->tag;
}

static inline void scst_cmd_set_tag(struct scst_cmd *cmd, uint64_t tag)
{
        cmd->tag = tag;
}

/*
 * Get/Set functions for cmd's target private data.
 * Variant with *_lock must be used if target driver uses
 * scst_find_cmd() to avoid race with it, except inside scst_find_cmd()'s
 * callback, where lock is already taken.
 */
static inline void *scst_cmd_get_tgt_priv(struct scst_cmd *cmd)
{
        return cmd->tgt_priv;
}

static inline void scst_cmd_set_tgt_priv(struct scst_cmd *cmd, void *val)
{
        cmd->tgt_priv = val;
}

void *scst_cmd_get_tgt_priv_lock(struct scst_cmd *cmd);
void scst_cmd_set_tgt_priv_lock(struct scst_cmd *cmd, void *val);

/*
 * Get/Set functions for tgt_need_alloc_data_buf flag
 */
static inline int scst_cmd_get_tgt_need_alloc_data_buf(struct scst_cmd *cmd)
{
        return cmd->tgt_need_alloc_data_buf;
}

static inline void scst_cmd_set_tgt_need_alloc_data_buf(struct scst_cmd *cmd)
{
        cmd->tgt_need_alloc_data_buf = 1;
}

/*
 * Get/Set functions for tgt_data_buf_alloced flag
 */
static inline int scst_cmd_get_tgt_data_buff_alloced(struct scst_cmd *cmd)
{
        return cmd->tgt_data_buf_alloced;
}

static inline void scst_cmd_set_tgt_data_buff_alloced(struct scst_cmd *cmd)
{
        cmd->tgt_data_buf_alloced = 1;
}

/*
 * Get/Set functions for dh_data_buf_alloced flag
 */
static inline int scst_cmd_get_dh_data_buff_alloced(struct scst_cmd *cmd)
{
        return cmd->dh_data_buf_alloced;
}

static inline void scst_cmd_set_dh_data_buff_alloced(struct scst_cmd *cmd)
{
        cmd->dh_data_buf_alloced = 1;
}

/*
 * Get/Set functions for no_sgv flag
 */
static inline int scst_cmd_get_no_sgv(struct scst_cmd *cmd)
{
        return cmd->no_sgv;
}

static inline void scst_cmd_set_no_sgv(struct scst_cmd *cmd)
{
        cmd->no_sgv = 1;
}

/*
 * Get/Set functions for tgt_sn
 */
static inline int scst_cmd_get_tgt_sn(struct scst_cmd *cmd)
{
        BUG_ON(!cmd->tgt_sn_set);
        return cmd->tgt_sn;
}

static inline void scst_cmd_set_tgt_sn(struct scst_cmd *cmd, uint32_t tgt_sn)
{
        cmd->tgt_sn_set = 1;
        cmd->tgt_sn = tgt_sn;
}

/*
 * Returns 1 if the cmd was aborted, so its status is invalid and no
 * reply shall be sent to the remote initiator. A target driver should
 * only clear internal resources, associated with cmd.
 */
static inline int scst_cmd_aborted(struct scst_cmd *cmd)
{
        return test_bit(SCST_CMD_ABORTED, &cmd->cmd_flags) &&
                !test_bit(SCST_CMD_ABORTED_OTHER, &cmd->cmd_flags);
}

/* Returns sense data format for cmd's dev */
static inline bool scst_get_cmd_dev_d_sense(struct scst_cmd *cmd)
{
        return (cmd->dev != NULL) ? cmd->dev->d_sense : 0;
}

/*
 * Get/Set functions for expected data direction, transfer length
 * and its validity flag
 */
static inline int scst_cmd_is_expected_set(struct scst_cmd *cmd)
{
        return cmd->expected_values_set;
}

static inline scst_data_direction scst_cmd_get_expected_data_direction(
        struct scst_cmd *cmd)
{
        return cmd->expected_data_direction;
}

static inline int scst_cmd_get_expected_transfer_len(
        struct scst_cmd *cmd)
{
        return cmd->expected_transfer_len;
}

static inline int scst_cmd_get_expected_in_transfer_len(
        struct scst_cmd *cmd)
{
        return cmd->expected_in_transfer_len;
}

static inline void scst_cmd_set_expected(struct scst_cmd *cmd,
        scst_data_direction expected_data_direction,
        int expected_transfer_len)
{
        cmd->expected_data_direction = expected_data_direction;
        cmd->expected_transfer_len = expected_transfer_len;
        cmd->expected_values_set = 1;
}

static inline void scst_cmd_set_expected_in_transfer_len(struct scst_cmd *cmd,
        int expected_in_transfer_len)
{
        WARN_ON(!cmd->expected_values_set);
        cmd->expected_in_transfer_len = expected_in_transfer_len;
}

/*
 * Get/clear functions for cmd's may_need_dma_sync
 */
static inline int scst_get_may_need_dma_sync(struct scst_cmd *cmd)
{
        return cmd->may_need_dma_sync;
}

static inline void scst_clear_may_need_dma_sync(struct scst_cmd *cmd)
{
        cmd->may_need_dma_sync = 0;
}

/*
 * Get/set functions for cmd's delivery_status. It is one of
 * SCST_CMD_DELIVERY_* constants. It specifies the status of the
 * command's delivery to initiator.
 */
static inline int scst_get_delivery_status(struct scst_cmd *cmd)
{
        return cmd->delivery_status;
}

static inline void scst_set_delivery_status(struct scst_cmd *cmd,
        int delivery_status)
{
        cmd->delivery_status = delivery_status;
}

/*
 * Get/Set function for mgmt cmd's target private data
 */
static inline void *scst_mgmt_cmd_get_tgt_priv(struct scst_mgmt_cmd *mcmd)
{
        return mcmd->tgt_priv;
}

static inline void scst_mgmt_cmd_set_tgt_priv(struct scst_mgmt_cmd *mcmd,
        void *val)
{
        mcmd->tgt_priv = val;
}

/* Returns mgmt cmd's completition status (SCST_MGMT_STATUS_* constants) */
static inline int scst_mgmt_cmd_get_status(struct scst_mgmt_cmd *mcmd)
{
        return mcmd->status;
}

/* Returns mgmt cmd's TM fn */
static inline int scst_mgmt_cmd_get_fn(struct scst_mgmt_cmd *mcmd)
{
        return mcmd->fn;
}

/*
 * Called by dev handler's task_mgmt_fn() to notify SCST core that mcmd
 * is going to complete asynchronously.
 */
void scst_prepare_async_mcmd(struct scst_mgmt_cmd *mcmd);

/*
 * Called by dev handler to notify SCST core that async. mcmd is completed
 * with status "status".
 */
void scst_async_mcmd_completed(struct scst_mgmt_cmd *mcmd, int status);

/* Returns AEN's fn */
static inline int scst_aen_get_event_fn(struct scst_aen *aen)
{
        return aen->event_fn;
}

/* Returns AEN's session */
static inline struct scst_session *scst_aen_get_sess(struct scst_aen *aen)
{
        return aen->sess;
}

/* Returns AEN's LUN */
static inline uint64_t scst_aen_get_lun(struct scst_aen *aen)
{
        return aen->lun;
}

/* Returns SCSI AEN's sense */
static inline const uint8_t *scst_aen_get_sense(struct scst_aen *aen)
{
        return aen->aen_sense;
}

/* Returns SCSI AEN's sense length */
static inline int scst_aen_get_sense_len(struct scst_aen *aen)
{
        return aen->aen_sense_len;
}

/*
 * Get/set functions for AEN's delivery_status. It is one of
 * SCST_AEN_RES_* constants. It specifies the status of the
 * command's delivery to initiator.
 */
static inline int scst_get_aen_delivery_status(struct scst_aen *aen)
{
        return aen->delivery_status;
}

static inline void scst_set_aen_delivery_status(struct scst_aen *aen,
        int status)
{
        aen->delivery_status = status;
}

/*
 * Notifies SCST that the driver has sent the AEN and it
 * can be freed now. Don't forget to set the delivery status, if it
 * isn't success, using scst_set_aen_delivery_status() before calling
 * this function.
 */
void scst_aen_done(struct scst_aen *aen);

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24)

/*
 * The macro's sg_page(), sg_virt(), sg_init_table(), sg_assign_page() and
 * sg_set_page() have been introduced in the 2.6.24 kernel. The definitions
 * below are backports of the 2.6.24 macro's for older kernels. There is one
 * exception however: when compiling SCST on a system with a pre-2.6.24 kernel
 * (e.g. RHEL 5.x) where the OFED kernel headers have been installed, do not
 * define the backported macro's because OFED has already defined these.
 */

#ifndef __BACKPORT_LINUX_SCATTERLIST_H_TO_2_6_23__

static inline struct page *sg_page(struct scatterlist *sg)
{
        return sg->page;
}

static inline void *sg_virt(struct scatterlist *sg)
{
        return page_address(sg_page(sg)) + sg->offset;
}

static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
        memset(sgl, 0, sizeof(*sgl) * nents);
}

static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
{
        sg->page = page;
}

static inline void sg_set_page(struct scatterlist *sg, struct page *page,
                               unsigned int len, unsigned int offset)
{
        sg_assign_page(sg, page);
        sg->offset = offset;
        sg->length = len;
}

static inline struct scatterlist *sg_next(struct scatterlist *sg)
{
        sg++;
        return sg;
}

#endif /* __BACKPORT_LINUX_SCATTERLIST_H_TO_2_6_23__ */

#endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24) */

static inline void sg_clear(struct scatterlist *sg)
{
        memset(sg, 0, sizeof(*sg));
#ifdef CONFIG_DEBUG_SG
        sg->sg_magic = SG_MAGIC;
#endif
}

/*
 * Functions for access to the commands data (SG) buffer,
 * including HIGHMEM environment. Should be used instead of direct
 * access. Returns the mapped buffer length for success, 0 for EOD,
 * negative error code otherwise.
 *
 * "Buf" argument returns the mapped buffer
 *
 * The "put" function unmaps the buffer.
 */
static inline int __scst_get_buf(struct scst_cmd *cmd, struct scatterlist *sg,
        int sg_cnt, uint8_t **buf)
{
        int res = 0;
        int i = cmd->get_sg_buf_entry_num;

        *buf = NULL;

        if ((i >= sg_cnt) || unlikely(sg == NULL))
                goto out;

        *buf = page_address(sg_page(&sg[i]));
        *buf += sg[i].offset;

        res = sg[i].length;
        cmd->get_sg_buf_entry_num++;

out:
        return res;
}

static inline int scst_get_buf_first(struct scst_cmd *cmd, uint8_t **buf)
{
        cmd->get_sg_buf_entry_num = 0;
        cmd->may_need_dma_sync = 1;
        return __scst_get_buf(cmd, cmd->sg, cmd->sg_cnt, buf);
}

static inline int scst_get_buf_next(struct scst_cmd *cmd, uint8_t **buf)
{
        return __scst_get_buf(cmd, cmd->sg, cmd->sg_cnt, buf);
}

static inline void scst_put_buf(struct scst_cmd *cmd, void *buf)
{
        /* Nothing to do */
}

static inline int scst_get_in_buf_first(struct scst_cmd *cmd, uint8_t **buf)
{
        cmd->get_sg_buf_entry_num = 0;
        cmd->may_need_dma_sync = 1;
        return __scst_get_buf(cmd, cmd->in_sg, cmd->in_sg_cnt, buf);
}

static inline int scst_get_in_buf_next(struct scst_cmd *cmd, uint8_t **buf)
{
        return __scst_get_buf(cmd, cmd->in_sg, cmd->in_sg_cnt, buf);
}

static inline void scst_put_in_buf(struct scst_cmd *cmd, void *buf)
{
        /* Nothing to do */
}

/*
 * Returns approximate higher rounded buffers count that
 * scst_get_buf_[first|next]() return.
 */
static inline int scst_get_buf_count(struct scst_cmd *cmd)
{
        return (cmd->sg_cnt == 0) ? 1 : cmd->sg_cnt;
}

/*
 * Returns approximate higher rounded buffers count that
 * scst_get_in_buf_[first|next]() return.
 */
static inline int scst_get_in_buf_count(struct scst_cmd *cmd)
{
        return (cmd->in_sg_cnt == 0) ? 1 : cmd->in_sg_cnt;
}

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 23) && !defined(BACKPORT_LINUX_WORKQUEUE_TO_2_6_19)
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 20))
static inline int cancel_delayed_work_sync(struct delayed_work *work)
#else
static inline int cancel_delayed_work_sync(struct work_struct *work)
#endif
{
        int res;

        res = cancel_delayed_work(work);
        flush_scheduled_work();
        return res;
}
#endif

/*
 * Suspends and resumes any activity.
 * Function scst_suspend_activity() doesn't return 0, until there are any
 * active commands (state after SCST_CMD_STATE_INIT). If "interruptible"
 * is true, it returns after SCST_SUSPENDING_TIMEOUT or if it was interrupted
 * by a signal with the coresponding error status < 0. If "interruptible"
 * is false, it will wait virtually forever.
 *
 * New arriving commands stay in that state until scst_resume_activity()
 * is called.
 */
int scst_suspend_activity(bool interruptible);
void scst_resume_activity(void);

/*
 * Main SCST commands processing routing. Must be used only by dev handlers.
 * Argument atomic is true if function called in atomic context.
 */
void scst_process_active_cmd(struct scst_cmd *cmd, bool atomic);

/*
 * SCST commands processing routine, which should be called by dev handler
 * after its parse() callback returned SCST_CMD_STATE_STOP. Arguments
 * the same as for scst_process_active_cmd().
 */
void scst_post_parse_process_active_cmd(struct scst_cmd *cmd, bool atomic);

/*
 * Checks if command can be executed (reservations, etc.) or there are local
 * events, like pending UAs. Returns < 0 if command must be aborted, > 0 if
 * there is an event and command should be immediately completed, or 0
 * otherwise.
 *
 * !! Dev handlers implementing exec() callback must call this function there !!
 * !! just before the actual command's execution                              !!
 */
int scst_check_local_events(struct scst_cmd *cmd);

/*
 * Returns the next state of the SCSI target state machine in case if command's
 * completed abnormally.
 */
int scst_get_cmd_abnormal_done_state(const struct scst_cmd *cmd);

/*
 * Sets state of the SCSI target state machine in case if command's completed
 * abnormally.
 */
void scst_set_cmd_abnormal_done_state(struct scst_cmd *cmd);

struct scst_trace_log {
        unsigned int val;
        const char *token;
};

#ifdef CONFIG_SCST_PROC

/*
 * Returns target driver's root entry in SCST's /proc hierarchy.
 * The driver can create own files/directories here, which should
 * be deleted in the driver's release().
 */
struct proc_dir_entry *scst_proc_get_tgt_root(
        struct scst_tgt_template *vtt);

/*
 * Returns device handler's root entry in SCST's /proc hierarchy.
 * The driver can create own files/directories here, which should
 * be deleted in the driver's detach()/release().
 */
struct proc_dir_entry *scst_proc_get_dev_type_root(
        struct scst_dev_type *dtt);

/**
 ** Two library functions and the structure to help the drivers
 ** that use scst_debug.* facilities manage "trace_level" /proc entry.
 ** The functions service "standard" log levels and allow to work
 ** with driver specific levels, which should be passed inside as
 ** NULL-terminated array of struct scst_trace_log's, where:
 **   - val - the level's numeric value
 **   - token - its string representation
 **/

int scst_proc_log_entry_read(struct seq_file *seq, unsigned long log_level,
        const struct scst_trace_log *tbl);
int scst_proc_log_entry_write(struct file *file, const char __user *buf,
        unsigned long length, unsigned long *log_level,
        unsigned long default_level, const struct scst_trace_log *tbl);

/*
 * helper data structure and function to create proc entry.
 */
struct scst_proc_data {
        const struct file_operations seq_op;
        int (*show)(struct seq_file *, void *);
        void *data;
};

int scst_single_seq_open(struct inode *inode, struct file *file);

struct proc_dir_entry *scst_create_proc_entry(struct proc_dir_entry *root,
        const char *name, struct scst_proc_data *pdata);

#define SCST_DEF_RW_SEQ_OP(x)                          \
        .seq_op = {                                    \
                .owner          = THIS_MODULE,         \
                .open           = scst_single_seq_open,\
                .read           = seq_read,            \
                .write          = x,                   \
                .llseek         = seq_lseek,           \
                .release        = single_release,      \
        },

#else /* CONFIG_SCST_PROC */

/*
 * Returns target driver's root sysfs kobject.
 * The driver can create own files/directories/links here.
 */
static inline struct kobject *scst_sysfs_get_tgtt_kobj(
        struct scst_tgt_template *tgtt)
{
        return &tgtt->tgtt_kobj;
}

/*
 * Returns target's root sysfs kobject.
 * The driver can create own files/directories/links here.
 */
static inline struct kobject *scst_sysfs_get_tgt_kobj(
        struct scst_tgt *tgt)
{
        return &tgt->tgt_kobj;
}

/*
 * Returns device handler's root sysfs kobject.
 * The driver can create own files/directories/links here.
 */
static inline struct kobject *scst_sysfs_get_devt_kobj(
        struct scst_dev_type *devt)
{
        return &devt->devt_kobj;
}

/*
 * Returns device's root sysfs kobject.
 * The driver can create own files/directories/links here.
 */
static inline struct kobject *scst_sysfs_get_dev_kobj(
        struct scst_device *dev)
{
        return &dev->dev_kobj;
}

#endif /* CONFIG_SCST_PROC */

/* Returns target name */
static inline const char *scst_get_tgt_name(const struct scst_tgt *tgt)
{
        return tgt->tgt_name;
}

/*
 * Adds and deletes (stops) num of global SCST's threads. Returns 0 on
 * success, error code otherwise.
 */
int scst_add_global_threads(int num);
void scst_del_global_threads(int num);

int scst_alloc_sense(struct scst_cmd *cmd, int atomic);
int scst_alloc_set_sense(struct scst_cmd *cmd, int atomic,
        const uint8_t *sense, unsigned int len);

/*
 * Sets the corresponding field in the sense buffer taking sense type
 * into account. Returns resulting sense length.
 */
int scst_set_sense(uint8_t *buffer, int len, bool d_sense,
        int key, int asc, int ascq);

/*
 * Returns true if the sense is valid and carrying a Unit Attention or
 * false otherwise.
 */
bool scst_is_ua_sense(const uint8_t *sense, int len);

/*
 * Returnes true if sense matches to (key, asc, ascq) and false otherwise.
 * Valid_mask is one or several SCST_SENSE_*_VALID constants setting valid
 * (key, asc, ascq) values.
 */
bool scst_analyze_sense(const uint8_t *sense, int len,
        unsigned int valid_mask, int key, int asc, int ascq);

/*
 * Returnes a pseudo-random number for debugging purposes. Available only in
 * the DEBUG build.
 */
unsigned long scst_random(void);

/*
 * Sets response data length for cmd and truncates its SG vector accordingly.
 * The cmd->resp_data_len must not be set directly, it must be set only
 * using this function. Value of resp_data_len must be <= cmd->bufflen.
 */
void scst_set_resp_data_len(struct scst_cmd *cmd, int resp_data_len);

/*
 * Get/put global ref counter that prevents from entering into suspended
 * activities stage, so protects from any global management operations.
 */
void scst_get(void);
void scst_put(void);

/*
 * Cmd ref counters
 */
void scst_cmd_get(struct scst_cmd *cmd);
void scst_cmd_put(struct scst_cmd *cmd);

/*
 * Allocates and returns pointer to SG vector with data size "size".
 * In *count returned the count of entries in the vector.
 * Returns NULL for failure.
 */
struct scatterlist *scst_alloc(int size, gfp_t gfp_mask, int *count);

/* Frees SG vector returned by scst_alloc() */
void scst_free(struct scatterlist *sg, int count);

/*
 * Adds local to the current thread data to tgt_dev
 * (they will be local for the tgt_dev and current thread).
 */
void scst_add_thr_data(struct scst_tgt_dev *tgt_dev,
        struct scst_thr_data_hdr *data,
        void (*free_fn) (struct scst_thr_data_hdr *data));

/* Deletes all local to threads data from tgt_dev */
void scst_del_all_thr_data(struct scst_tgt_dev *tgt_dev);

/* Deletes all local to threads data from all tgt_dev's of the dev */
void scst_dev_del_all_thr_data(struct scst_device *dev);

/* Finds local to the thread data. Returns NULL, if they not found. */
struct scst_thr_data_hdr *__scst_find_thr_data(struct scst_tgt_dev *tgt_dev,
        struct task_struct *tsk);

/* Finds local to the current thread data. Returns NULL, if they not found. */
static inline struct scst_thr_data_hdr *scst_find_thr_data(
        struct scst_tgt_dev *tgt_dev)
{
        return __scst_find_thr_data(tgt_dev, current);
}

static inline void scst_thr_data_get(struct scst_thr_data_hdr *data)
{
        atomic_inc(&data->ref);
}

static inline void scst_thr_data_put(struct scst_thr_data_hdr *data)
{
        if (atomic_dec_and_test(&data->ref))
                data->free_fn(data);
}

/**
 ** Generic parse() support routines.
 ** Done via pointer on functions to avoid unneeded dereferences on
 ** the fast path.
 **/

/* Calculates and returns block shift for the given sector size */
int scst_calc_block_shift(int sector_size);

/* Generic parse() for SBC (disk) devices */
int scst_sbc_generic_parse(struct scst_cmd *cmd,
        int (*get_block_shift)(struct scst_cmd *cmd));

/* Generic parse() for MMC (cdrom) devices */
int scst_cdrom_generic_parse(struct scst_cmd *cmd,
        int (*get_block_shift)(struct scst_cmd *cmd));

/* Generic parse() for MO disk devices */
int scst_modisk_generic_parse(struct scst_cmd *cmd,
        int (*get_block_shift)(struct scst_cmd *cmd));

/* Generic parse() for tape devices */
int scst_tape_generic_parse(struct scst_cmd *cmd,
        int (*get_block_size)(struct scst_cmd *cmd));

/* Generic parse() for changer devices */
int scst_changer_generic_parse(struct scst_cmd *cmd,
        int (*nothing)(struct scst_cmd *cmd));

/* Generic parse() for "processor" devices */
int scst_processor_generic_parse(struct scst_cmd *cmd,
        int (*nothing)(struct scst_cmd *cmd));

/* Generic parse() for RAID devices */
int scst_raid_generic_parse(struct scst_cmd *cmd,
        int (*nothing)(struct scst_cmd *cmd));

/**
 ** Generic dev_done() support routines.
 ** Done via pointer on functions to avoid unneeded dereferences on
 ** the fast path.
 **/

/* Generic dev_done() for block devices */
int scst_block_generic_dev_done(struct scst_cmd *cmd,
        void (*set_block_shift)(struct scst_cmd *cmd, int block_shift));

/* Generic dev_done() for tape devices */
int scst_tape_generic_dev_done(struct scst_cmd *cmd,
        void (*set_block_size)(struct scst_cmd *cmd, int block_size));

/*
 * Issues a MODE SENSE for control mode page data and sets the corresponding
 * dev's parameter from it. Returns 0 on success and not 0 otherwise.
 */
int scst_obtain_device_parameters(struct scst_device *dev);

/*
 * Has to be put here open coded, because Linux doesn't have equivalent, which
 * allows exclusive wake ups of threads in LIFO order. We need it to let (yet)
 * unneeded threads sleep and not pollute CPU cache by their stacks.
 */
static inline void add_wait_queue_exclusive_head(wait_queue_head_t *q,
        wait_queue_t *wait)
{
        unsigned long flags;

        wait->flags |= WQ_FLAG_EXCLUSIVE;
        spin_lock_irqsave(&q->lock, flags);
        __add_wait_queue(q, wait);
        spin_unlock_irqrestore(&q->lock, flags);
}

#endif /* __SCST_H */