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+#ifndef _SCSI_GENERIC_H
+#define _SCSI_GENERIC_H
+
+#include <linux/compiler.h>
+
+/*
+   History:
+    Started: Aug 9 by Lawrence Foard (entropy@world.std.com), to allow user
+     process control of SCSI devices.
+    Development Sponsored by Killy Corp. NY NY
+Original driver (sg.h):
+*       Copyright (C) 1992 Lawrence Foard
+Version 2 and 3 extensions to driver:
+*       Copyright (C) 1998 - 2003 Douglas Gilbert
+
+    Version: 3.5.29 (20030529)
+    This version is for 2.5 series kernels.
+
+    Changes since 3.5.28 (20030308)
+        - fix bug introduced in version 3.1.24 (last segment of sgat list)
+    Changes since 3.5.27 (20020812)
+        - remove procfs entries: hosts, host_hdr + host_strs (now in sysfs)
+        - add sysfs sg driver params: def_reserved_size, allow_dio, version
+        - new boot option: "sg_allow_dio" and module parameter: "allow_dio"
+        - multiple internal changes due to scsi subsystem rework        
+    Changes since 3.5.26 (20020708)
+        - re-add direct IO using Kai Makisara's work
+        - re-tab to 8, start using C99-isms
+        - simplify memory management
+    Changes since 3.5.25 (20020504)
+        - driverfs additions
+        - copy_to/from_user() fixes [William Stinson]
+        - disable kiobufs support
+
+    For a full changelog see http://www.torque.net/sg
+
+Map of SG verions to the Linux kernels in which they appear:
+       ----------        ----------------------------------
+       original          all kernels < 2.2.6
+       2.1.40            2.2.20
+       3.0.x             optional version 3 sg driver for 2.2 series
+       3.1.17++          2.4.0++
+       3.5.23++          2.5.0++
+
+Major new features in SG 3.x driver (cf SG 2.x drivers)
+        - SG_IO ioctl() combines function if write() and read()
+        - new interface (sg_io_hdr_t) but still supports old interface
+        - scatter/gather in user space, direct IO, and mmap supported
+
+ The normal action of this driver is to use the adapter (HBA) driver to DMA
+ data into kernel buffers and then use the CPU to copy the data into the 
+ user space (vice versa for writes). That is called "indirect" IO due to 
+ the double handling of data. There are two methods offered to remove the
+ redundant copy: 1) direct IO which uses the kernel kiobuf mechanism and 
+ 2) using the mmap() system call to map the reserve buffer (this driver has 
+ one reserve buffer per fd) into the user space. Both have their advantages.
+ In terms of absolute speed mmap() is faster. If speed is not a concern, 
+ indirect IO should be fine. Read the documentation for more information.
+
+ ** N.B. To use direct IO 'echo 1 > /proc/scsi/sg/allow_dio' may be
+         needed. That pseudo file's content is defaulted to 0. **
+ 
+ Historical note: this SCSI pass-through driver has been known as "sg" for 
+ a decade. In broader kernel discussions "sg" is used to refer to scatter
+ gather techniques. The context should clarify which "sg" is referred to.
+
+ Documentation
+ =============
+ A web site for the SG device driver can be found at:
+        http://www.torque.net/sg  [alternatively check the MAINTAINERS file]
+ The documentation for the sg version 3 driver can be found at:
+        http://www.torque.net/sg/p/sg_v3_ho.html
+ This is a rendering from DocBook source [change the extension to "sgml"
+ or "xml"]. There are renderings in "ps", "pdf", "rtf" and "txt" (soon).
+
+ The older, version 2 documents discuss the original sg interface in detail:
+        http://www.torque.net/sg/p/scsi-generic.txt
+        http://www.torque.net/sg/p/scsi-generic_long.txt
+ A version of this document (potentially out of date) may also be found in
+ the kernel source tree, probably at:
+        Documentation/scsi/scsi-generic.txt .
+
+ Utility and test programs are available at the sg web site. They are 
+ bundled as sg_utils (for the lk 2.2 series) and sg3_utils (for the
+ lk 2.4 series).
+
+ There is a HOWTO on the Linux SCSI subsystem in the lk 2.4 series at:
+        http://www.linuxdoc.org/HOWTO/SCSI-2.4-HOWTO
+*/
+
+
+/* New interface introduced in the 3.x SG drivers follows */
+
+typedef struct sg_iovec /* same structure as used by readv() Linux system */
+{                       /* call. It defines one scatter-gather element. */
+    void __user *iov_base;      /* Starting address  */
+    size_t iov_len;             /* Length in bytes  */
+} sg_iovec_t;
+
+
+typedef struct sg_io_hdr
+{
+    int interface_id;           /* [i] 'S' for SCSI generic (required) */
+    int dxfer_direction;        /* [i] data transfer direction  */
+    unsigned char cmd_len;      /* [i] SCSI command length ( <= 16 bytes) */
+    unsigned char mx_sb_len;    /* [i] max length to write to sbp */
+    unsigned short iovec_count; /* [i] 0 implies no scatter gather */
+    unsigned int dxfer_len;     /* [i] byte count of data transfer */
+    void __user *dxferp;        /* [i], [*io] points to data transfer memory
+                                              or scatter gather list */
+    unsigned char __user *cmdp; /* [i], [*i] points to command to perform */
+    void __user *sbp;           /* [i], [*o] points to sense_buffer memory */
+    unsigned int timeout;       /* [i] MAX_UINT->no timeout (unit: millisec) */
+    unsigned int flags;         /* [i] 0 -> default, see SG_FLAG... */
+    int pack_id;                /* [i->o] unused internally (normally) */
+    void __user * usr_ptr;      /* [i->o] unused internally */
+    unsigned char status;       /* [o] scsi status */
+    unsigned char masked_status;/* [o] shifted, masked scsi status */
+    unsigned char msg_status;   /* [o] messaging level data (optional) */
+    unsigned char sb_len_wr;    /* [o] byte count actually written to sbp */
+    unsigned short host_status; /* [o] errors from host adapter */
+    unsigned short driver_status;/* [o] errors from software driver */
+    int resid;                  /* [o] dxfer_len - actual_transferred */
+    unsigned int duration;      /* [o] time taken by cmd (unit: millisec) */
+    unsigned int info;          /* [o] auxiliary information */
+} sg_io_hdr_t;  /* 64 bytes long (on i386) */
+
+#define SG_INTERFACE_ID_ORIG 'S'
+
+/* Use negative values to flag difference from original sg_header structure */
+#define SG_DXFER_NONE (-1)      /* e.g. a SCSI Test Unit Ready command */
+#define SG_DXFER_TO_DEV (-2)    /* e.g. a SCSI WRITE command */
+#define SG_DXFER_FROM_DEV (-3)  /* e.g. a SCSI READ command */
+#define SG_DXFER_TO_FROM_DEV (-4) /* treated like SG_DXFER_FROM_DEV with the
+                                   additional property than during indirect
+                                   IO the user buffer is copied into the
+                                   kernel buffers before the transfer */
+#define SG_DXFER_UNKNOWN (-5)   /* Unknown data direction */
+
+/* following flag values can be "or"-ed together */
+#define SG_FLAG_DIRECT_IO 1     /* default is indirect IO */
+#define SG_FLAG_UNUSED_LUN_INHIBIT 2   /* default is overwrite lun in SCSI */
+                                /* command block (when <= SCSI_2) */
+#define SG_FLAG_MMAP_IO 4       /* request memory mapped IO */
+#define SG_FLAG_NO_DXFER 0x10000 /* no transfer of kernel buffers to/from */
+                                /* user space (debug indirect IO) */
+
+/* following 'info' values are "or"-ed together */
+#define SG_INFO_OK_MASK 0x1
+#define SG_INFO_OK 0x0          /* no sense, host nor driver "noise" */
+#define SG_INFO_CHECK 0x1       /* something abnormal happened */
+
+#define SG_INFO_DIRECT_IO_MASK 0x6
+#define SG_INFO_INDIRECT_IO 0x0 /* data xfer via kernel buffers (or no xfer) */
+#define SG_INFO_DIRECT_IO 0x2   /* direct IO requested and performed */
+#define SG_INFO_MIXED_IO 0x4    /* part direct, part indirect IO */
+
+
+typedef struct sg_scsi_id { /* used by SG_GET_SCSI_ID ioctl() */
+    int host_no;        /* as in "scsi<n>" where 'n' is one of 0, 1, 2 etc */
+    int channel;
+    int scsi_id;        /* scsi id of target device */
+    int lun;
+    int scsi_type;      /* TYPE_... defined in scsi/scsi.h */
+    short h_cmd_per_lun;/* host (adapter) maximum commands per lun */
+    short d_queue_depth;/* device (or adapter) maximum queue length */
+    int unused[2];      /* probably find a good use, set 0 for now */
+} sg_scsi_id_t; /* 32 bytes long on i386 */
+
+typedef struct sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */
+    char req_state;     /* 0 -> not used, 1 -> written, 2 -> ready to read */
+    char orphan;        /* 0 -> normal request, 1 -> from interruped SG_IO */
+    char sg_io_owned;   /* 0 -> complete with read(), 1 -> owned by SG_IO */
+    char problem;       /* 0 -> no problem detected, 1 -> error to report */
+    int pack_id;        /* pack_id associated with request */
+    void __user *usr_ptr;     /* user provided pointer (in new interface) */
+    unsigned int duration; /* millisecs elapsed since written (req_state==1)
+                              or request duration (req_state==2) */
+    int unused;
+} sg_req_info_t; /* 20 bytes long on i386 */
+
+
+/* IOCTLs: Those ioctls that are relevant to the SG 3.x drivers follow.
+ [Those that only apply to the SG 2.x drivers are at the end of the file.]
+ (_GET_s yield result via 'int *' 3rd argument unless otherwise indicated) */
+
+#define SG_EMULATED_HOST 0x2203 /* true for emulated host adapter (ATAPI) */
+
+/* Used to configure SCSI command transformation layer for ATAPI devices */
+/* Only supported by the ide-scsi driver */
+#define SG_SET_TRANSFORM 0x2204 /* N.B. 3rd arg is not pointer but value: */
+                      /* 3rd arg = 0 to disable transform, 1 to enable it */
+#define SG_GET_TRANSFORM 0x2205
+
+#define SG_SET_RESERVED_SIZE 0x2275  /* request a new reserved buffer size */
+#define SG_GET_RESERVED_SIZE 0x2272  /* actual size of reserved buffer */
+
+/* The following ioctl has a 'sg_scsi_id_t *' object as its 3rd argument. */
+#define SG_GET_SCSI_ID 0x2276   /* Yields fd's bus, chan, dev, lun + type */
+/* SCSI id information can also be obtained from SCSI_IOCTL_GET_IDLUN */
+
+/* Override host setting and always DMA using low memory ( <16MB on i386) */
+#define SG_SET_FORCE_LOW_DMA 0x2279  /* 0-> use adapter setting, 1-> force */
+#define SG_GET_LOW_DMA 0x227a   /* 0-> use all ram for dma; 1-> low dma ram */
+
+/* When SG_SET_FORCE_PACK_ID set to 1, pack_id is input to read() which
+   tries to fetch a packet with a matching pack_id, waits, or returns EAGAIN.
+   If pack_id is -1 then read oldest waiting. When ...FORCE_PACK_ID set to 0
+   then pack_id ignored by read() and oldest readable fetched. */
+#define SG_SET_FORCE_PACK_ID 0x227b
+#define SG_GET_PACK_ID 0x227c /* Yields oldest readable pack_id (or -1) */
+
+#define SG_GET_NUM_WAITING 0x227d /* Number of commands awaiting read() */
+
+/* Yields max scatter gather tablesize allowed by current host adapter */
+#define SG_GET_SG_TABLESIZE 0x227F  /* 0 implies can't do scatter gather */
+
+#define SG_GET_VERSION_NUM 0x2282 /* Example: version 2.1.34 yields 20134 */
+
+/* Returns -EBUSY if occupied. 3rd argument pointer to int (see next) */
+#define SG_SCSI_RESET 0x2284
+/* Associated values that can be given to SG_SCSI_RESET follow */
+#define         SG_SCSI_RESET_NOTHING   0
+#define         SG_SCSI_RESET_DEVICE    1
+#define         SG_SCSI_RESET_BUS       2
+#define         SG_SCSI_RESET_HOST      3
+
+/* synchronous SCSI command ioctl, (only in version 3 interface) */
+#define SG_IO 0x2285   /* similar effect as write() followed by read() */
+
+#define SG_GET_REQUEST_TABLE 0x2286   /* yields table of active requests */
+
+/* How to treat EINTR during SG_IO ioctl(), only in SG 3.x series */
+#define SG_SET_KEEP_ORPHAN 0x2287 /* 1 -> hold for read(), 0 -> drop (def) */
+#define SG_GET_KEEP_ORPHAN 0x2288
+
+/* yields scsi midlevel's access_count for this SCSI device */
+#define SG_GET_ACCESS_COUNT 0x2289  
+
+
+#define SG_SCATTER_SZ (8 * 4096)  /* PAGE_SIZE not available to user */
+/* Largest size (in bytes) a single scatter-gather list element can have.
+   The value must be a power of 2 and <= (PAGE_SIZE * 32) [131072 bytes on
+   i386]. The minimum value is PAGE_SIZE. If scatter-gather not supported
+   by adapter then this value is the largest data block that can be
+   read/written by a single scsi command. The user can find the value of
+   PAGE_SIZE by calling getpagesize() defined in unistd.h . */
+
+#define SG_DEFAULT_RETRIES 0
+
+/* Defaults, commented if they differ from original sg driver */
+#define SG_DEF_FORCE_LOW_DMA 0  /* was 1 -> memory below 16MB on i386 */
+#define SG_DEF_FORCE_PACK_ID 0
+#define SG_DEF_KEEP_ORPHAN 0
+#define SG_DEF_RESERVED_SIZE SG_SCATTER_SZ /* load time option */
+
+/* maximum outstanding requests, write() yields EDOM if exceeded */
+#define SG_MAX_QUEUE 16
+
+#define SG_BIG_BUFF SG_DEF_RESERVED_SIZE    /* for backward compatibility */
+
+/* Alternate style type names, "..._t" variants preferred */
+typedef struct sg_io_hdr Sg_io_hdr;
+typedef struct sg_io_vec Sg_io_vec;
+typedef struct sg_scsi_id Sg_scsi_id;
+typedef struct sg_req_info Sg_req_info;
+
+
+/* vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv */
+/*   The older SG interface based on the 'sg_header' structure follows.   */
+/* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ */
+
+#define SG_MAX_SENSE 16   /* this only applies to the sg_header interface */
+
+struct sg_header
+{
+    int pack_len;    /* [o] reply_len (ie useless), ignored as input */
+    int reply_len;   /* [i] max length of expected reply (inc. sg_header) */
+    int pack_id;     /* [io] id number of packet (use ints >= 0) */
+    int result;      /* [o] 0==ok, else (+ve) Unix errno (best ignored) */
+    unsigned int twelve_byte:1;
+        /* [i] Force 12 byte command length for group 6 & 7 commands  */
+    unsigned int target_status:5;   /* [o] scsi status from target */
+    unsigned int host_status:8;     /* [o] host status (see "DID" codes) */
+    unsigned int driver_status:8;   /* [o] driver status+suggestion */
+    unsigned int other_flags:10;    /* unused */
+    unsigned char sense_buffer[SG_MAX_SENSE]; /* [o] Output in 3 cases:
+           when target_status is CHECK_CONDITION or
+           when target_status is COMMAND_TERMINATED or
+           when (driver_status & DRIVER_SENSE) is true. */
+};      /* This structure is 36 bytes long on i386 */
+
+
+/* IOCTLs: The following are not required (or ignored) when the sg_io_hdr_t
+           interface is used. They are kept for backward compatibility with
+           the original and version 2 drivers. */
+
+#define SG_SET_TIMEOUT 0x2201  /* unit: jiffies (10ms on i386) */
+#define SG_GET_TIMEOUT 0x2202  /* yield timeout as _return_ value */
+
+/* Get/set command queuing state per fd (default is SG_DEF_COMMAND_Q.
+   Each time a sg_io_hdr_t object is seen on this file descriptor, this
+   command queuing flag is set on (overriding the previous setting). */
+#define SG_GET_COMMAND_Q 0x2270   /* Yields 0 (queuing off) or 1 (on) */
+#define SG_SET_COMMAND_Q 0x2271   /* Change queuing state with 0 or 1 */
+
+/* Turn on/off error sense trace (1 and 0 respectively, default is off).
+   Try using: "# cat /proc/scsi/sg/debug" instead in the v3 driver */
+#define SG_SET_DEBUG 0x227e    /* 0 -> turn off debug */
+
+#define SG_NEXT_CMD_LEN 0x2283  /* override SCSI command length with given
+                   number on the next write() on this file descriptor */
+
+
+/* Defaults, commented if they differ from original sg driver */
+#ifdef __KERNEL__
+#define SG_DEFAULT_TIMEOUT_USER (60*USER_HZ) /* HZ == 'jiffies in 1 second' */
+#else
+#define SG_DEFAULT_TIMEOUT      (60*HZ)      /* HZ == 'jiffies in 1 second' */
+#endif
+
+#define SG_DEF_COMMAND_Q 0     /* command queuing is always on when
+                                  the new interface is used */
+#define SG_DEF_UNDERRUN_FLAG 0
+
+#endif