hosts.h

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/*
 *  hosts.h Copyright (C) 1992 Drew Eckhardt
 *          Copyright (C) 1993, 1994, 1995, 1998, 1999 Eric Youngdale
 *
 *  mid to low-level SCSI driver interface header
 *      Initial versions: Drew Eckhardt
 *      Subsequent revisions: Eric Youngdale
 *
 *  <[e-mail]>
 *
 *	 Modified by Eric Youngdale [e-mail] to
 *	 add scatter-gather, multiple outstanding request, and other
 *	 enhancements.
 *
 *  Further modified by Eric Youngdale to support multiple host adapters
 *  of the same type.
 *
 *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
 */

#ifndef _HOSTS_H
#define _HOSTS_H

/*
    $Header: /vger/u4/cvs/linux/drivers/scsi/hosts.h,v 1.6 1997/01/19 23:07:13 davem Exp $
*/

#include <linux/config.h>
#include <linux/proc_fs.h>

/* It is senseless to set SG_ALL any higher than this - the performance
 *  does not get any better, and it wastes memory
 */
#define SG_NONE 0
#define SG_ALL 0xff

#define DISABLE_CLUSTERING 0
#define ENABLE_CLUSTERING 1

/* 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.
 */

/*
 * The Scsi_Host_Template type has all that is needed to interface with a SCSI
 * host in a device independent matter.	 There is one entry for each different
 * type of host adapter that is supported on the system.
 */

typedef struct scsi_disk Disk;

typedef struct	SHT
{

    /* Used with loadable modules so we can construct a linked list. */
    struct SHT * next;

    /* Used with loadable modules so that we know when it is safe to unload */
    struct module * module;

    /* The pointer to the /proc/scsi directory entry */
    struct proc_dir_entry *proc_dir;

    /* proc-fs info function.
     * 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. Check eata_dma_proc.c for reference
     */
    int (*proc_info)(char *, char **, off_t, int, int, int);

    /*
     * The name pointer is a pointer to the name of the SCSI
     * device detected.
     */
    const char *name;

    /*
     * The detect function shall return non zero on detection,
     * indicating the number of host adapters of this particular
     * type were found.	 It should also
     * initialize all data necessary for this particular
     * SCSI driver.  It is passed the host number, so this host
     * knows where the first entry is in the scsi_hosts[] array.
     *
     * Note that the detect routine MUST not call any of the mid level
     * functions to queue commands because things are not guaranteed
     * to be set up yet.  The detect routine can send commands to
     * the host adapter as long as the program control will not be
     * passed to scsi.c in the processing of the command.  Note
     * especially that scsi_malloc/scsi_free must not be called.
     */
    int (* detect)(struct SHT *);

    int (*revoke)(Scsi_Device *);

    /* Used with loadable modules to unload the host structures.  Note:
     * there is a default action built into the modules code which may
     * be sufficient for most host adapters.  Thus you may not have to supply
     * this at all.
     */
    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.
     */
    const char *(* info)(struct Scsi_Host *);

    /*
     * ioctl interface
     */
    int (*ioctl)(Scsi_Device *dev, int cmd, void *arg);

    /*
     * The command function takes a target, a command (this is a SCSI
     * command formatted as per the SCSI spec, nothing strange), a
     * data buffer pointer, and data buffer length pointer.  The return
     * is a status int, bit fielded as follows :
     * Byte What
     * 0    SCSI status code
     * 1    SCSI 1 byte message
     * 2    host error return.
     * 3    mid level error return
     */
    int (* command)(Scsi_Cmnd *);

    /*
     * The QueueCommand function works in a similar manner
     * to the command function.	 It takes an additional parameter,
     * void (* done)(int host, int code) which is passed the host
     * # and exit result when the command is complete.
     * Host number is the POSITION IN THE hosts array of THIS
     * host adapter.
     *
     * The done() function must only be called after QueueCommand() 
     * has returned.
     */
    int (* queuecommand)(Scsi_Cmnd *, void (*done)(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.
     */
     int (*eh_strategy_handler)(struct Scsi_Host *);
     int (*eh_abort_handler)(Scsi_Cmnd *);
     int (*eh_device_reset_handler)(Scsi_Cmnd *);
     int (*eh_bus_reset_handler)(Scsi_Cmnd *);
     int (*eh_host_reset_handler)(Scsi_Cmnd *);

    /*
     * Since the mid level driver handles time outs, etc, we want to
     * be able to abort the current command.  Abort returns 0 if the
     * abortion was successful.	 The field SCpnt->abort reason
     * can be filled in with the appropriate reason why we wanted
     * the abort in the first place, and this will be used
     * in the mid-level code instead of the host_byte().
     * If non-zero, the code passed to it
     * will be used as the return code, otherwise
     * DID_ABORT  should be returned.
     *
     * Note that the scsi driver should "clean up" after itself,
     * resetting the bus, etc.	if necessary.
     *
     * NOTE - this interface is depreciated, and will go away.  Use
     * the eh_ routines instead.
     */
    int (* abort)(Scsi_Cmnd *);

    /*
     * The reset function will reset the SCSI bus.  Any executing
     * commands should fail with a DID_RESET in the host byte.
     * The Scsi_Cmnd  is passed so that the reset routine can figure
     * out which host adapter should be reset, and also which command
     * within the command block was responsible for the reset in
     * the first place.	 Some hosts do not implement a reset function,
     * and these hosts must call scsi_request_sense(SCpnt) to keep
     * the command alive.
     *
     * NOTE - this interface is depreciated, and will go away.  Use
     * the eh_ routines instead.
     */
    int (* reset)(Scsi_Cmnd *, unsigned int);

    /*
     * This function is used to select synchronous communications,
     * which will result in a higher data throughput.  Not implemented
     * yet.
     */
    int (* slave_attach)(int, 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 number, list (heads, sectors, cylinders)
     */
    int (* bios_param)(Disk *, kdev_t, int []);


    /*
     * Used to set the queue depth for a specific device.
     */
    void (*select_queue_depths)(struct Scsi_Host *, Scsi_Device *);

    /*
     * 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.
     */
    short unsigned int sg_tablesize;

    /*
     * 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;

    /*
     * 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 if this driver uses the new error handling code.  This flag is
     * really only temporary until all of the other drivers get converted
     * to use the new error handling code.
     */
    unsigned use_new_eh_code:1;

    /*