include/scsi/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

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	 * Status:  OBSOLETE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	 * Status: OBSOLETE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
	 * 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);

	/*
	 * 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 []);

	/*
	 * 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 *);

	/*
	 * 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;

	/*
	 * 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).
	 */