scsi_host.h

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#ifndef _SCSI_SCSI_HOST_H
#define _SCSI_SCSI_HOST_H

#include <linux/device.h>
#include <linux/list.h>
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <scsi/scsi.h>

struct request_queue;
struct block_device;
struct completion;
struct module;
struct scsi_cmnd;
struct scsi_device;
struct scsi_target;
struct Scsi_Host;
struct scsi_host_cmd_pool;
struct scsi_transport_template;
struct blk_queue_tags;


/*
 * The various choices mean:
 * NONE: Self evident.  Host adapter is not capable of scatter-gather.
 * ALL:  Means that the host adapter module can do scatter-gather,
 *   and that there is no limit to the size of the table to which
 *   we scatter/gather data.  The value we set here is the maximum
 *   single element sglist.  To use chained sglists, the adapter
 *   has to set a value beyond ALL (and correctly use the chain
 *   handling API.
 * Anything else:  Indicates the maximum number of chains that can be
 *   used in one scatter-gather request.
 */
#define SG_NONE 0
#define SG_ALL  SCSI_MAX_SG_SEGMENTS

#define MODE_UNKNOWN 0x00
#define MODE_INITIATOR 0x01
#define MODE_TARGET 0x02

#define DISABLE_CLUSTERING 0
#define ENABLE_CLUSTERING 1

enum {
    SCSI_QDEPTH_DEFAULT,    /* default requested change, e.g. from sysfs */
    SCSI_QDEPTH_QFULL,  /* scsi-ml requested due to queue full */
    SCSI_QDEPTH_RAMP_UP,    /* scsi-ml requested due to threshold event */
};

struct scsi_host_template {
    struct module *module;
    const char *name;

    /*
     * Used to initialize old-style drivers.  For new-style drivers
     * just perform all work in your module initialization function.
     *
     * Status:  OBSOLETE
     */
    int (* detect)(struct scsi_host_template *);

    /*
     * Used as unload callback for hosts with old-style drivers.
     *
     * Status: OBSOLETE
     */
    int (* release)(struct Scsi_Host *);

    /*
     * The info function will return whatever useful information the
     * developer sees fit.  If not provided, then the name field will
     * be used instead.
     *
     * Status: OPTIONAL
     */
    const char *(* info)(struct Scsi_Host *);

    /*
     * Ioctl interface
     *
     * Status: OPTIONAL
     */
    int (* ioctl)(struct scsi_device *dev, int cmd, void __user *arg);


#ifdef CONFIG_COMPAT
    /* 
     * Compat handler. Handle 32bit ABI.
     * When unknown ioctl is passed return -ENOIOCTLCMD.
     *
     * Status: OPTIONAL
     */
    int (* compat_ioctl)(struct scsi_device *dev, int cmd, void __user *arg);
#endif

    /*
     * The queuecommand function is used to queue up a scsi
     * command block to the LLDD.  When the driver finished
     * processing the command the done callback is invoked.
     *
     * If queuecommand returns 0, then the HBA has accepted the
     * command.  The done() function must be called on the command
     * when the driver has finished with it. (you may call done on the
     * command before queuecommand returns, but in this case you
     * *must* return 0 from queuecommand).
     *
     * Queuecommand may also reject the command, in which case it may
     * not touch the command and must not call done() for it.
     *
     * There are two possible rejection returns:
     *
     *   SCSI_MLQUEUE_DEVICE_BUSY: Block this device temporarily, but
     *   allow commands to other devices serviced by this host.
     *
     *   SCSI_MLQUEUE_HOST_BUSY: Block all devices served by this
     *   host temporarily.
     *
         * For compatibility, any other non-zero return is treated the
         * same as SCSI_MLQUEUE_HOST_BUSY.
     *
     * NOTE: "temporarily" means either until the next command for#
     * this device/host completes, or a period of time determined by
     * I/O pressure in the system if there are no other outstanding
     * commands.
     *
     * STATUS: REQUIRED
     */
    int (* queuecommand)(struct Scsi_Host *, struct scsi_cmnd *);

    /*
     * The transfer functions are used to queue a scsi command to
     * the LLD. When the driver is finished processing the command
     * the done callback is invoked.
     *
     * This is called to inform the LLD to transfer
     * scsi_bufflen(cmd) bytes. scsi_sg_count(cmd) speciefies the
     * number of scatterlist entried in the command and
     * scsi_sglist(cmd) returns the scatterlist.
     *
     * return values: see queuecommand
     *
     * If the LLD accepts the cmd, it should set the result to an
     * appropriate value when completed before calling the done function.
     *
     * STATUS: REQUIRED FOR TARGET DRIVERS
     */
    /* TODO: rename */
    int (* transfer_response)(struct scsi_cmnd *,
                  void (*done)(struct scsi_cmnd *));

    /*
     * This is an error handling strategy routine.  You don't need to
     * define one of these if you don't want to - there is a default
     * routine that is present that should work in most cases.  For those
     * driver authors that have the inclination and ability to write their
     * own strategy routine, this is where it is specified.  Note - the
     * strategy routine is *ALWAYS* run in the context of the kernel eh
     * thread.  Thus you are guaranteed to *NOT* be in an interrupt
     * handler when you execute this, and you are also guaranteed to
     * *NOT* have any other commands being queued while you are in the
     * strategy routine. When you return from this function, operations
     * return to normal.
     *
     * See scsi_error.c scsi_unjam_host for additional comments about
     * what this function should and should not be attempting to do.
     *
     * Status: REQUIRED (at least one of them)
     */
    int (* eh_abort_handler)(struct scsi_cmnd *);
    int (* eh_device_reset_handler)(struct scsi_cmnd *);
    int (* eh_target_reset_handler)(struct scsi_cmnd *);
    int (* eh_bus_reset_handler)(struct scsi_cmnd *);
    int (* eh_host_reset_handler)(struct scsi_cmnd *);

    /*
     * Before the mid layer attempts to scan for a new device where none
     * currently exists, it will call this entry in your driver.  Should
     * your driver need to allocate any structs or perform any other init
     * items in order to send commands to a currently unused target/lun
     * combo, then this is where you can perform those allocations.  This
     * is specifically so that drivers won't have to perform any kind of
     * "is this a new device" checks in their queuecommand routine,
     * thereby making the hot path a bit quicker.
     *
     * Return values: 0 on success, non-0 on failure
     *
     * Deallocation:  If we didn't find any devices at this ID, you will
     * get an immediate call to slave_destroy().  If we find something
     * here then you will get a call to slave_configure(), then the
     * device will be used for however long it is kept around, then when
     * the device is removed from the system (or * possibly at reboot
     * time), you will then get a call to slave_destroy().  This is
     * assuming you implement slave_configure and slave_destroy.
     * However, if you allocate memory and hang it off the device struct,
     * then you must implement the slave_destroy() routine at a minimum
     * in order to avoid leaking memory
     * each time a device is tore down.
     *
     * Status: OPTIONAL
     */
    int (* slave_alloc)(struct scsi_device *);

    /*
     * Once the device has responded to an INQUIRY and we know the
     * device is online, we call into the low level driver with the
     * struct scsi_device *.  If the low level device driver implements
     * this function, it *must* perform the task of setting the queue
     * depth on the device.  All other tasks are optional and depend
     * on what the driver supports and various implementation details.
     * 
     * Things currently recommended to be handled at this time include:
     *
     * 1.  Setting the device queue depth.  Proper setting of this is
     *     described in the comments for scsi_adjust_queue_depth.
     * 2.  Determining if the device supports the various synchronous
     *     negotiation protocols.  The device struct will already have
     *     responded to INQUIRY and the results of the standard items
     *     will have been shoved into the various device flag bits, eg.
     *     device->sdtr will be true if the device supports SDTR messages.
     * 3.  Allocating command structs that the device will need.
     * 4.  Setting the default timeout on this device (if needed).
     * 5.  Anything else the low level driver might want to do on a device
     *     specific setup basis...
     * 6.  Return 0 on success, non-0 on error.  The device will be marked
     *     as offline on error so that no access will occur.  If you return
     *     non-0, your slave_destroy routine will never get called for this
     *     device, so don't leave any loose memory hanging around, clean
     *     up after yourself before returning non-0
     *
     * Status: OPTIONAL
     */
    int (* slave_configure)(struct scsi_device *);

    /*
     * Immediately prior to deallocating the device and after all activity
     * has ceased the mid layer calls this point so that the low level
     * driver may completely detach itself from the scsi device and vice
     * versa.  The low level driver is responsible for freeing any memory
     * it allocated in the slave_alloc or slave_configure calls. 
     *
     * Status: OPTIONAL
     */
    void (* slave_destroy)(struct scsi_device *);

    /*
     * Before the mid layer attempts to scan for a new device attached
     * to a target where no target currently exists, it will call this
     * entry in your driver.  Should your driver need to allocate any
     * structs or perform any other init items in order to send commands
     * to a currently unused target, then this is where you can perform
     * those allocations.
     *
     * Return values: 0 on success, non-0 on failure
     *
     * Status: OPTIONAL
     */
    int (* target_alloc)(struct scsi_target *);

    /*
     * Immediately prior to deallocating the target structure, and
     * after all activity to attached scsi devices has ceased, the
     * midlayer calls this point so that the driver may deallocate
     * and terminate any references to the target.
     *
     * Status: OPTIONAL
     */
    void (* target_destroy)(struct scsi_target *);

    /*
     * If a host has the ability to discover targets on its own instead
     * of scanning the entire bus, it can fill in this function and
     * call scsi_scan_host().  This function will be called periodically
     * until it returns 1 with the scsi_host and the elapsed time of
     * the scan in jiffies.
     *
     * Status: OPTIONAL
     */
    int (* scan_finished)(struct Scsi_Host *, unsigned long);

    /*
     * If the host wants to be called before the scan starts, but
     * after the midlayer has set up ready for the scan, it can fill
     * in this function.
     *
     * Status: OPTIONAL
     */
    void (* scan_start)(struct Scsi_Host *);

    /*
     * Fill in this function to allow the queue depth of this host
     * to be changeable (on a per device basis).  Returns either
     * the current queue depth setting (may be different from what
     * was passed in) or an error.  An error should only be
     * returned if the requested depth is legal but the driver was
     * unable to set it.  If the requested depth is illegal, the
     * driver should set and return the closest legal queue depth.
     *
     * Status: OPTIONAL
     */
    int (* change_queue_depth)(struct scsi_device *, int, int);

    /*
     * Fill in this function to allow the changing of tag types
     * (this also allows the enabling/disabling of tag command
     * queueing).  An error should only be returned if something
     * went wrong in the driver while trying to set the tag type.
     * If the driver doesn't support the requested tag type, then
     * it should set the closest type it does support without
     * returning an error.  Returns the actual tag type set.
     *
     * Status: OPTIONAL
     */
    int (* change_queue_type)(struct scsi_device *, int);

    /*
     * This function determines the BIOS parameters for a given
     * harddisk.  These tend to be numbers that are made up by
     * the host adapter.  Parameters:
     * size, device, list (heads, sectors, cylinders)
     *
     * Status: OPTIONAL
     */
    int (* bios_param)(struct scsi_device *, struct block_device *,
            sector_t, int []);

    /*
     * This function is called when one or more partitions on the
     * device reach beyond the end of the device.
     *
     * Status: OPTIONAL
     */
    void (*unlock_native_capacity)(struct scsi_device *);

    /*
     * Can be used to export driver statistics and other infos to the
     * world outside the kernel ie. userspace and it also provides an
     * interface to feed the driver with information.
     *
     * Status: OBSOLETE
     */
    int (*proc_info)(struct Scsi_Host *, char *, char **, off_t, int, int);

    /*
     * This is an optional routine that allows the transport to become
     * involved when a scsi io timer fires. The return value tells the
     * timer routine how to finish the io timeout handling:
     * EH_HANDLED:      I fixed the error, please complete the command
     * EH_RESET_TIMER:  I need more time, reset the timer and
     *          begin counting again
     * EH_NOT_HANDLED   Begin normal error recovery
     *
     * Status: OPTIONAL
     */
    enum blk_eh_timer_return (*eh_timed_out)(struct scsi_cmnd *);

    /* This is an optional routine that allows transport to initiate
     * LLD adapter or firmware reset using sysfs attribute.
     *
     * Return values: 0 on success, -ve value on failure.
     *
     * Status: OPTIONAL
     */

    int (*host_reset)(struct Scsi_Host *shost, int reset_type);
#define SCSI_ADAPTER_RESET  1
#define SCSI_FIRMWARE_RESET 2


    /*
     * Name of proc directory
     */
    const char *proc_name;

    /*
     * Used to store the procfs directory if a driver implements the
     * proc_info method.
     */
    struct proc_dir_entry *proc_dir;

    /*
     * This determines if we will use a non-interrupt driven
     * or an interrupt driven scheme.  It is set to the maximum number
     * of simultaneous commands a given host adapter will accept.
     */
    int can_queue;

    /*
     * In many instances, especially where disconnect / reconnect are
     * supported, our host also has an ID on the SCSI bus.  If this is
     * the case, then it must be reserved.  Please set this_id to -1 if
     * your setup is in single initiator mode, and the host lacks an
     * ID.
     */
    int this_id;

    /*
     * This determines the degree to which the host adapter is capable
     * of scatter-gather.
     */
    unsigned short sg_tablesize;
    unsigned short sg_prot_tablesize;

    /*
     * Set this if the host adapter has limitations beside segment count.
     */
    unsigned short max_sectors;

    /*
     * DMA scatter gather segment boundary limit. A segment crossing this
     * boundary will be split in two.
     */
    unsigned long dma_boundary;

    /*
     * This specifies "machine infinity" for host templates which don't
     * limit the transfer size.  Note this limit represents an absolute
     * maximum, and may be over the transfer limits allowed for
     * individual devices (e.g. 256 for SCSI-1).
     */
#define SCSI_DEFAULT_MAX_SECTORS    1024

    /*
     * True if this host adapter can make good use of linked commands.
     * This will allow more than one command to be queued to a given
     * unit on a given host.  Set this to the maximum number of command
     * blocks to be provided for each device.  Set this to 1 for one
     * command block per lun, 2 for two, etc.  Do not set this to 0.
     * You should make sure that the host adapter will do the right thing
     * before you try setting this above 1.
     */
    short cmd_per_lun;

    /*
     * present contains counter indicating how many boards of this
     * type were found when we did the scan.
     */
    unsigned char present;

    /*
     * This specifies the mode that a LLD supports.
     */
    unsigned supported_mode:2;

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

    /*
     * True if this host adapter can make good use of clustering.
     * I originally thought that if the tablesize was large that it
     * was a waste of CPU cycles to prepare a cluster list, but
     * it works out that the Buslogic is faster if you use a smaller
     * number of segments (i.e. use clustering).  I guess it is
     * inefficient.
     */
    unsigned use_clustering:1;

    /*
     * True for emulated SCSI host adapters (e.g. ATAPI).
     */
    unsigned emulated:1;

    /*
     * True if the low-level driver performs its own reset-settle delays.
     */
    unsigned skip_settle_delay:1;

    /*
     * True if we are using ordered write support.
     */
    unsigned ordered_tag:1;

    /*
     * Countdown for host blocking with no commands outstanding.
     */
    unsigned int max_host_blocked;

    /*
     * Default value for the blocking.  If the queue is empty,
     * host_blocked counts down in the request_fn until it restarts
     * host operations as zero is reached.  
     *
     * FIXME: This should probably be a value in the template
     */
#define SCSI_DEFAULT_HOST_BLOCKED   7

    /*
     * Pointer to the sysfs class properties for this host, NULL terminated.
     */
    struct device_attribute **shost_attrs;

    /*
     * Pointer to the SCSI device properties for this host, NULL terminated.
     */
    struct device_attribute **sdev_attrs;

    /*
     * List of hosts per template.
     *
     * This is only for use by scsi_module.c for legacy templates.
     * For these access to it is synchronized implicitly by
     * module_init/module_exit.
     */
    struct list_head legacy_hosts;

    /*
     * Vendor Identifier associated with the host
     *
     * Note: When specifying vendor_id, be sure to read the
     *   Vendor Type and ID formatting requirements specified in
     *   scsi_netlink.h
     */
    u64 vendor_id;
};

/*
 * Temporary #define for host lock push down. Can be removed when all
 * drivers have been updated to take advantage of unlocked
 * queuecommand.
 *
 */
#define DEF_SCSI_QCMD(func_name) \
    int func_name(struct Scsi_Host *shost, struct scsi_cmnd *cmd)   \
    {                               \
        unsigned long irq_flags;                \
        int rc;                         \
        spin_lock_irqsave(shost->host_lock, irq_flags);     \
        scsi_cmd_get_serial(shost, cmd);            \
        rc = func_name##_lck (cmd, cmd->scsi_done);         \
        spin_unlock_irqrestore(shost->host_lock, irq_flags);    \
        return rc;                      \
    }


/*
 * shost state: If you alter this, you also need to alter scsi_sysfs.c
 * (for the ascii descriptions) and the state model enforcer:
 * scsi_host_set_state()
 */
enum scsi_host_state {
    SHOST_CREATED = 1,
    SHOST_RUNNING,
    SHOST_CANCEL,
    SHOST_DEL,
    SHOST_RECOVERY,
    SHOST_CANCEL_RECOVERY,
    SHOST_DEL_RECOVERY,
};

struct Scsi_Host {
    /*
     * __devices is protected by the host_lock, but you should
     * usually use scsi_device_lookup / shost_for_each_device
     * to access it and don't care about locking yourself.
     * In the rare case of beeing in irq context you can use
     * their __ prefixed variants with the lock held. NEVER
     * access this list directly from a driver.
     */
    struct list_head    __devices;
    struct list_head    __targets;
    
    struct scsi_host_cmd_pool *cmd_pool;
    spinlock_t      free_list_lock;
    struct list_head    free_list; /* backup store of cmd structs */
    struct list_head    starved_list;

    spinlock_t      default_lock;
    spinlock_t      *host_lock;

    struct mutex        scan_mutex;/* serialize scanning activity */

    struct list_head    eh_cmd_q;
    struct task_struct    * ehandler;  /* Error recovery thread. */
    struct completion     * eh_action; /* Wait for specific actions on the
                          host. */
    wait_queue_head_t       host_wait;
    struct scsi_host_template *hostt;
    struct scsi_transport_template *transportt;

    /*
     * Area to keep a shared tag map (if needed, will be
     * NULL if not).
     */
    struct blk_queue_tag    *bqt;

    /*
     * The following two fields are protected with host_lock;
     * however, eh routines can safely access during eh processing
     * without acquiring the lock.
     */
    unsigned int host_busy;        /* commands actually active on low-level */
    unsigned int host_failed;      /* commands that failed. */
    unsigned int host_eh_scheduled;    /* EH scheduled without command */
    
    unsigned int host_no;  /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */
    int resetting; /* if set, it means that last_reset is a valid value */
    unsigned long last_reset;

    /*
     * These three parameters can be used to allow for wide scsi,
     * and for host adapters that support multiple busses
     * The first two should be set to 1 more than the actual max id
     * or lun (i.e. 8 for normal systems).
     */
    unsigned int max_id;
    unsigned int max_lun;
    unsigned int max_channel;

    /*
     * This is a unique identifier that must be assigned so that we
     * have some way of identifying each detected host adapter properly
     * and uniquely.  For hosts that do not support more than one card
     * in the system at one time, this does not need to be set.  It is
     * initialized to 0 in scsi_register.
     */
    unsigned int unique_id;

    /*
     * The maximum length of SCSI commands that this host can accept.
     * Probably 12 for most host adapters, but could be 16 for others.
     * or 260 if the driver supports variable length cdbs.
     * For drivers that don't set this field, a value of 12 is
     * assumed.
     */
    unsigned short max_cmd_len;

    int this_id;
    int can_queue;
    short cmd_per_lun;
    short unsigned int sg_tablesize;
    short unsigned int sg_prot_tablesize;
    short unsigned int max_sectors;
    unsigned long dma_boundary;
    /* 
     * Used to assign serial numbers to the cmds.
     * Protected by the host lock.
     */
    unsigned long cmd_serial_number;
    
    unsigned active_mode:2;
    unsigned unchecked_isa_dma:1;
    unsigned use_clustering:1;
    unsigned use_blk_tcq:1;

    /*
     * Host has requested that no further requests come through for the
     * time being.
     */
    unsigned host_self_blocked:1;
    
    /*
     * Host uses correct SCSI ordering not PC ordering. The bit is
     * set for the minority of drivers whose authors actually read
     * the spec ;).
     */
    unsigned reverse_ordering:1;

    /*
     * Ordered write support
     */
    unsigned ordered_tag:1;

    /* Task mgmt function in progress */
    unsigned tmf_in_progress:1;

    /* Asynchronous scan in progress */
    unsigned async_scan:1;

    /* Don't resume host in EH */
    unsigned eh_noresume:1;

    /*
     * Optional work queue to be utilized by the transport
     */
    char work_q_name[20];
    struct workqueue_struct *work_q;

    /*
     * Host has rejected a command because it was busy.
     */
    unsigned int host_blocked;

    /*
     * Value host_blocked counts down from
     */
    unsigned int max_host_blocked;

    /* Protection Information */
    unsigned int prot_capabilities;
    unsigned char prot_guard_type;

    /*
     * q used for scsi_tgt msgs, async events or any other requests that
     * need to be processed in userspace
     */
    struct request_queue *uspace_req_q;

    /* legacy crap */
    unsigned long base;
    unsigned long io_port;
    unsigned char n_io_port;
    unsigned char dma_channel;
    unsigned int  irq;
    

    enum scsi_host_state shost_state;

    /* ldm bits */
    struct device       shost_gendev, shost_dev;

    /*
     * List of hosts per template.
     *
     * This is only for use by scsi_module.c for legacy templates.
     * For these access to it is synchronized implicitly by
     * module_init/module_exit.
     */
    struct list_head sht_legacy_list;

    /*
     * Points to the transport data (if any) which is allocated
     * separately
     */
    void *shost_data;

    /*
     * Points to the physical bus device we'd use to do DMA
     * Needed just in case we have virtual hosts.
     */
    struct device *dma_dev;

    /*
     * We should ensure that this is aligned, both for better performance
     * and also because some compilers (m68k) don't automatically force
     * alignment to a long boundary.
     */
    unsigned long hostdata[0]  /* Used for storage of host specific stuff */
        __attribute__ ((aligned (sizeof(unsigned long))));
};

#define     class_to_shost(d)   \
    container_of(d, struct Scsi_Host, shost_dev)

#define shost_printk(prefix, shost, fmt, a...)  \
    dev_printk(prefix, &(shost)->shost_gendev, fmt, ##a)

static inline void *shost_priv(struct Scsi_Host *shost)
{
    return (void *)shost->hostdata;
}

int scsi_is_host_device(const struct device *);

static inline struct Scsi_Host *dev_to_shost(struct device *dev)
{
    while (!scsi_is_host_device(dev)) {
        if (!dev->parent)
            return NULL;
        dev = dev->parent;
    }
    return container_of(dev, struct Scsi_Host, shost_gendev);
}

static inline int scsi_host_in_recovery(struct Scsi_Host *shost)
{
    return shost->shost_state == SHOST_RECOVERY ||
        shost->shost_state == SHOST_CANCEL_RECOVERY ||
        shost->shost_state == SHOST_DEL_RECOVERY ||
        shost->tmf_in_progress;
}

extern int scsi_queue_work(struct Scsi_Host *, struct work_struct *);
extern void scsi_flush_work(struct Scsi_Host *);

extern struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *, int);
extern int __must_check scsi_add_host_with_dma(struct Scsi_Host *,
                           struct device *,
                           struct device *);
extern void scsi_scan_host(struct Scsi_Host *);
extern void scsi_rescan_device(struct device *);
extern void scsi_remove_host(struct Scsi_Host *);
extern struct Scsi_Host *scsi_host_get(struct Scsi_Host *);
extern void scsi_host_put(struct Scsi_Host *t);
extern struct Scsi_Host *scsi_host_lookup(unsigned short);
extern const char *scsi_host_state_name(enum scsi_host_state);
extern void scsi_cmd_get_serial(struct Scsi_Host *, struct scsi_cmnd *);

extern u64 scsi_calculate_bounce_limit(struct Scsi_Host *);

static inline int __must_check scsi_add_host(struct Scsi_Host *host,
                         struct device *dev)
{
    return scsi_add_host_with_dma(host, dev, dev);
}

static inline struct device *scsi_get_device(struct Scsi_Host *shost)
{
        return shost->shost_gendev.parent;
}

static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
{
    return shost->shost_state == SHOST_RUNNING ||
           shost->shost_state == SHOST_RECOVERY;
}

extern void scsi_unblock_requests(struct Scsi_Host *);
extern void scsi_block_requests(struct Scsi_Host *);

struct class_container;

extern struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
                        void (*) (struct request_queue *));
/*
 * These two functions are used to allocate and free a pseudo device
 * which will connect to the host adapter itself rather than any
 * physical device.  You must deallocate when you are done with the
 * thing.  This physical pseudo-device isn't real and won't be available
 * from any high-level drivers.
 */
extern void scsi_free_host_dev(struct scsi_device *);
extern struct scsi_device *scsi_get_host_dev(struct Scsi_Host *);

/*
 * DIF defines the exchange of protection information between
 * initiator and SBC block device.
 *
 * DIX defines the exchange of protection information between OS and
 * initiator.
 */
enum scsi_host_prot_capabilities {
    SHOST_DIF_TYPE1_PROTECTION = 1 << 0, /* T10 DIF Type 1 */
    SHOST_DIF_TYPE2_PROTECTION = 1 << 1, /* T10 DIF Type 2 */
    SHOST_DIF_TYPE3_PROTECTION = 1 << 2, /* T10 DIF Type 3 */

    SHOST_DIX_TYPE0_PROTECTION = 1 << 3, /* DIX between OS and HBA only */
    SHOST_DIX_TYPE1_PROTECTION = 1 << 4, /* DIX with DIF Type 1 */
    SHOST_DIX_TYPE2_PROTECTION = 1 << 5, /* DIX with DIF Type 2 */
    SHOST_DIX_TYPE3_PROTECTION = 1 << 6, /* DIX with DIF Type 3 */
};

/*
 * SCSI hosts which support the Data Integrity Extensions must
 * indicate their capabilities by setting the prot_capabilities using
 * this call.
 */
static inline void scsi_host_set_prot(struct Scsi_Host *shost, unsigned int mask)
{
    shost->prot_capabilities = mask;
}

static inline unsigned int scsi_host_get_prot(struct Scsi_Host *shost)
{
    return shost->prot_capabilities;
}

static inline int scsi_host_prot_dma(struct Scsi_Host *shost)
{
    return shost->prot_capabilities >= SHOST_DIX_TYPE0_PROTECTION;
}

static inline unsigned int scsi_host_dif_capable(struct Scsi_Host *shost, unsigned int target_type)
{
    static unsigned char cap[] = { 0,
                       SHOST_DIF_TYPE1_PROTECTION,
                       SHOST_DIF_TYPE2_PROTECTION,
                       SHOST_DIF_TYPE3_PROTECTION };

    if (target_type > SHOST_DIF_TYPE3_PROTECTION)
        return 0;

    return shost->prot_capabilities & cap[target_type] ? target_type : 0;
}

static inline unsigned int scsi_host_dix_capable(struct Scsi_Host *shost, unsigned int target_type)
{
#if defined(CONFIG_BLK_DEV_INTEGRITY)
    static unsigned char cap[] = { SHOST_DIX_TYPE0_PROTECTION,
                       SHOST_DIX_TYPE1_PROTECTION,
                       SHOST_DIX_TYPE2_PROTECTION,
                       SHOST_DIX_TYPE3_PROTECTION };

    if (target_type > SHOST_DIX_TYPE3_PROTECTION)
        return 0;

    return shost->prot_capabilities & cap[target_type];
#endif
    return 0;
}

/*
 * All DIX-capable initiators must support the T10-mandated CRC
 * checksum.  Controllers can optionally implement the IP checksum
 * scheme which has much lower impact on system performance.  Note
 * that the main rationale for the checksum is to match integrity
 * metadata with data.  Detecting bit errors are a job for ECC memory
 * and buses.
 */

enum scsi_host_guard_type {
    SHOST_DIX_GUARD_CRC = 1 << 0,
    SHOST_DIX_GUARD_IP  = 1 << 1,
};

static inline void scsi_host_set_guard(struct Scsi_Host *shost, unsigned char type)
{
    shost->prot_guard_type = type;
}

static inline unsigned char scsi_host_get_guard(struct Scsi_Host *shost)
{
    return shost->prot_guard_type;
}

/* legacy interfaces */
extern struct Scsi_Host *scsi_register(struct scsi_host_template *, int);
extern void scsi_unregister(struct Scsi_Host *);
extern int scsi_host_set_state(struct Scsi_Host *, enum scsi_host_state);

#endif /* _SCSI_SCSI_HOST_H */