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scsi_host.h

#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>

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.
 * Anything else:  Indicates the maximum number of chains that can be
 *     used in one scatter-gather request.
 */
#define SG_NONE 0
#define SG_ALL 0xff

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

#define DISABLE_CLUSTERING 0
#define ENABLE_CLUSTERING 1

#define DISABLE_SG_CHAINING 0
#define ENABLE_SG_CHAINING 1

enum scsi_eh_timer_return {
      EH_NOT_HANDLED,
      EH_HANDLED,
      EH_RESET_TIMER,
};


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       * Status:  OBSOLETE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       * Status: OBSOLETE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_cmnd *,
                       void (*done)(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
       * cmd->request_bufflen bytes. The cmd->use_sg speciefies the
       * number of scatterlist entried in the command and
       * cmd->request_buffer contains 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_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.
       */
      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.
       *
       */
      int (* change_queue_depth)(struct scsi_device *, 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.
       */
      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 []);

      /*
       * 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 scsi_eh_timer_return (* eh_timed_out)(struct scsi_cmnd *);

      /*
       * 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;

      /*
       * 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;

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

      /*
       * true if the low-level driver can support sg chaining. this
       * will be removed eventually when all the drivers are
       * converted to support sg chaining.
       *
       * Status: OBSOLETE
       */
      unsigned use_sg_chaining: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 class_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;
};

/*
 * 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 short 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.
       * For drivers that don't set this field, a value of 12 is
       * assumed.  I am leaving this as a number rather than a bit
       * because you never know what subsequent SCSI standards might do
       * (i.e. could there be a 20 byte or a 24-byte command a few years
       * down the road?).  
       */
      unsigned char max_cmd_len;

      int this_id;
      int can_queue;
      short cmd_per_lun;
      short unsigned int sg_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;
      unsigned use_sg_chaining: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;

      /*
       * Optional work queue to be utilized by the transport
       */
      char work_q_name[KOBJ_NAME_LEN];
      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;

      /*
       * 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;
      struct class_device     shost_classdev;

      /*
       * 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;

      /*
       * 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_classdev)

#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(struct Scsi_Host *, 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 u64 scsi_calculate_bounce_limit(struct Scsi_Host *);

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

/**
 * scsi_host_scan_allowed - Is scanning of this host allowed
 * @shost:  Pointer to Scsi_Host.
 **/
static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
{
      return shost->shost_state == SHOST_RUNNING;
}

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 *);

/* 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 */

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