linux/include/scsi/sg.h
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   1#ifndef _SCSI_GENERIC_H
   2#define _SCSI_GENERIC_H
   3
   4#include <linux/compiler.h>
   5
   6/*
   7   History:
   8    Started: Aug 9 by Lawrence Foard (entropy@world.std.com), to allow user
   9     process control of SCSI devices.
  10    Development Sponsored by Killy Corp. NY NY
  11Original driver (sg.h):
  12*       Copyright (C) 1992 Lawrence Foard
  13Version 2 and 3 extensions to driver:
  14*       Copyright (C) 1998 - 2006 Douglas Gilbert
  15
  16    Version: 3.5.34 (20060920)
  17    This version is for 2.6 series kernels.
  18
  19    For a full changelog see http://www.torque.net/sg
  20
  21Map of SG verions to the Linux kernels in which they appear:
  22       ----------        ----------------------------------
  23       original          all kernels < 2.2.6
  24       2.1.40            2.2.20
  25       3.0.x             optional version 3 sg driver for 2.2 series
  26       3.1.17++          2.4.0++
  27       3.5.30++          2.6.0++
  28
  29Major new features in SG 3.x driver (cf SG 2.x drivers)
  30        - SG_IO ioctl() combines function if write() and read()
  31        - new interface (sg_io_hdr_t) but still supports old interface
  32        - scatter/gather in user space, direct IO, and mmap supported
  33
  34 The normal action of this driver is to use the adapter (HBA) driver to DMA
  35 data into kernel buffers and then use the CPU to copy the data into the 
  36 user space (vice versa for writes). That is called "indirect" IO due to 
  37 the double handling of data. There are two methods offered to remove the
  38 redundant copy: 1) direct IO and 2) using the mmap() system call to map
  39 the reserve buffer (this driver has one reserve buffer per fd) into the
  40 user space. Both have their advantages.
  41 In terms of absolute speed mmap() is faster. If speed is not a concern, 
  42 indirect IO should be fine. Read the documentation for more information.
  43
  44 ** N.B. To use direct IO 'echo 1 > /proc/scsi/sg/allow_dio' or
  45         'echo 1 > /sys/module/sg/parameters/allow_dio' is needed.
  46         That attribute is 0 by default. **
  47 
  48 Historical note: this SCSI pass-through driver has been known as "sg" for 
  49 a decade. In broader kernel discussions "sg" is used to refer to scatter
  50 gather techniques. The context should clarify which "sg" is referred to.
  51
  52 Documentation
  53 =============
  54 A web site for the SG device driver can be found at:
  55        http://www.torque.net/sg  [alternatively check the MAINTAINERS file]
  56 The documentation for the sg version 3 driver can be found at:
  57        http://www.torque.net/sg/p/sg_v3_ho.html
  58 This is a rendering from DocBook source [change the extension to "sgml"
  59 or "xml"]. There are renderings in "ps", "pdf", "rtf" and "txt" (soon).
  60 The SG_IO ioctl is now found in other parts kernel (e.g. the block layer).
  61 For more information see http://www.torque.net/sg/sg_io.html
  62
  63 The older, version 2 documents discuss the original sg interface in detail:
  64        http://www.torque.net/sg/p/scsi-generic.txt
  65        http://www.torque.net/sg/p/scsi-generic_long.txt
  66 Also available: <kernel_source>/Documentation/scsi/scsi-generic.txt
  67
  68 Utility and test programs are available at the sg web site. They are 
  69 packaged as sg3_utils (for the lk 2.4 and 2.6 series) and sg_utils
  70 (for the lk 2.2 series).
  71*/
  72
  73#ifdef __KERNEL__
  74extern int sg_big_buff; /* for sysctl */
  75#endif
  76
  77/* New interface introduced in the 3.x SG drivers follows */
  78
  79typedef struct sg_iovec /* same structure as used by readv() Linux system */
  80{                       /* call. It defines one scatter-gather element. */
  81    void __user *iov_base;      /* Starting address  */
  82    size_t iov_len;             /* Length in bytes  */
  83} sg_iovec_t;
  84
  85
  86typedef struct sg_io_hdr
  87{
  88    int interface_id;           /* [i] 'S' for SCSI generic (required) */
  89    int dxfer_direction;        /* [i] data transfer direction  */
  90    unsigned char cmd_len;      /* [i] SCSI command length ( <= 16 bytes) */
  91    unsigned char mx_sb_len;    /* [i] max length to write to sbp */
  92    unsigned short iovec_count; /* [i] 0 implies no scatter gather */
  93    unsigned int dxfer_len;     /* [i] byte count of data transfer */
  94    void __user *dxferp;        /* [i], [*io] points to data transfer memory
  95                                              or scatter gather list */
  96    unsigned char __user *cmdp; /* [i], [*i] points to command to perform */
  97    void __user *sbp;           /* [i], [*o] points to sense_buffer memory */
  98    unsigned int timeout;       /* [i] MAX_UINT->no timeout (unit: millisec) */
  99    unsigned int flags;         /* [i] 0 -> default, see SG_FLAG... */
 100    int pack_id;                /* [i->o] unused internally (normally) */
 101    void __user * usr_ptr;      /* [i->o] unused internally */
 102    unsigned char status;       /* [o] scsi status */
 103    unsigned char masked_status;/* [o] shifted, masked scsi status */
 104    unsigned char msg_status;   /* [o] messaging level data (optional) */
 105    unsigned char sb_len_wr;    /* [o] byte count actually written to sbp */
 106    unsigned short host_status; /* [o] errors from host adapter */
 107    unsigned short driver_status;/* [o] errors from software driver */
 108    int resid;                  /* [o] dxfer_len - actual_transferred */
 109    unsigned int duration;      /* [o] time taken by cmd (unit: millisec) */
 110    unsigned int info;          /* [o] auxiliary information */
 111} sg_io_hdr_t;  /* 64 bytes long (on i386) */
 112
 113#define SG_INTERFACE_ID_ORIG 'S'
 114
 115/* Use negative values to flag difference from original sg_header structure */
 116#define SG_DXFER_NONE (-1)      /* e.g. a SCSI Test Unit Ready command */
 117#define SG_DXFER_TO_DEV (-2)    /* e.g. a SCSI WRITE command */
 118#define SG_DXFER_FROM_DEV (-3)  /* e.g. a SCSI READ command */
 119#define SG_DXFER_TO_FROM_DEV (-4) /* treated like SG_DXFER_FROM_DEV with the
 120                                   additional property than during indirect
 121                                   IO the user buffer is copied into the
 122                                   kernel buffers before the transfer */
 123#define SG_DXFER_UNKNOWN (-5)   /* Unknown data direction */
 124
 125/* following flag values can be "or"-ed together */
 126#define SG_FLAG_DIRECT_IO 1     /* default is indirect IO */
 127#define SG_FLAG_UNUSED_LUN_INHIBIT 2   /* default is overwrite lun in SCSI */
 128                                /* command block (when <= SCSI_2) */
 129#define SG_FLAG_MMAP_IO 4       /* request memory mapped IO */
 130#define SG_FLAG_NO_DXFER 0x10000 /* no transfer of kernel buffers to/from */
 131                                /* user space (debug indirect IO) */
 132
 133/* following 'info' values are "or"-ed together */
 134#define SG_INFO_OK_MASK 0x1
 135#define SG_INFO_OK 0x0          /* no sense, host nor driver "noise" */
 136#define SG_INFO_CHECK 0x1       /* something abnormal happened */
 137
 138#define SG_INFO_DIRECT_IO_MASK 0x6
 139#define SG_INFO_INDIRECT_IO 0x0 /* data xfer via kernel buffers (or no xfer) */
 140#define SG_INFO_DIRECT_IO 0x2   /* direct IO requested and performed */
 141#define SG_INFO_MIXED_IO 0x4    /* part direct, part indirect IO */
 142
 143
 144typedef struct sg_scsi_id { /* used by SG_GET_SCSI_ID ioctl() */
 145    int host_no;        /* as in "scsi<n>" where 'n' is one of 0, 1, 2 etc */
 146    int channel;
 147    int scsi_id;        /* scsi id of target device */
 148    int lun;
 149    int scsi_type;      /* TYPE_... defined in scsi/scsi.h */
 150    short h_cmd_per_lun;/* host (adapter) maximum commands per lun */
 151    short d_queue_depth;/* device (or adapter) maximum queue length */
 152    int unused[2];      /* probably find a good use, set 0 for now */
 153} sg_scsi_id_t; /* 32 bytes long on i386 */
 154
 155typedef struct sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */
 156    char req_state;     /* 0 -> not used, 1 -> written, 2 -> ready to read */
 157    char orphan;        /* 0 -> normal request, 1 -> from interruped SG_IO */
 158    char sg_io_owned;   /* 0 -> complete with read(), 1 -> owned by SG_IO */
 159    char problem;       /* 0 -> no problem detected, 1 -> error to report */
 160    int pack_id;        /* pack_id associated with request */
 161    void __user *usr_ptr;     /* user provided pointer (in new interface) */
 162    unsigned int duration; /* millisecs elapsed since written (req_state==1)
 163                              or request duration (req_state==2) */
 164    int unused;
 165} sg_req_info_t; /* 20 bytes long on i386 */
 166
 167
 168/* IOCTLs: Those ioctls that are relevant to the SG 3.x drivers follow.
 169 [Those that only apply to the SG 2.x drivers are at the end of the file.]
 170 (_GET_s yield result via 'int *' 3rd argument unless otherwise indicated) */
 171
 172#define SG_EMULATED_HOST 0x2203 /* true for emulated host adapter (ATAPI) */
 173
 174/* Used to configure SCSI command transformation layer for ATAPI devices */
 175/* Only supported by the ide-scsi driver */
 176#define SG_SET_TRANSFORM 0x2204 /* N.B. 3rd arg is not pointer but value: */
 177                      /* 3rd arg = 0 to disable transform, 1 to enable it */
 178#define SG_GET_TRANSFORM 0x2205
 179
 180#define SG_SET_RESERVED_SIZE 0x2275  /* request a new reserved buffer size */
 181#define SG_GET_RESERVED_SIZE 0x2272  /* actual size of reserved buffer */
 182
 183/* The following ioctl has a 'sg_scsi_id_t *' object as its 3rd argument. */
 184#define SG_GET_SCSI_ID 0x2276   /* Yields fd's bus, chan, dev, lun + type */
 185/* SCSI id information can also be obtained from SCSI_IOCTL_GET_IDLUN */
 186
 187/* Override host setting and always DMA using low memory ( <16MB on i386) */
 188#define SG_SET_FORCE_LOW_DMA 0x2279  /* 0-> use adapter setting, 1-> force */
 189#define SG_GET_LOW_DMA 0x227a   /* 0-> use all ram for dma; 1-> low dma ram */
 190
 191/* When SG_SET_FORCE_PACK_ID set to 1, pack_id is input to read() which
 192   tries to fetch a packet with a matching pack_id, waits, or returns EAGAIN.
 193   If pack_id is -1 then read oldest waiting. When ...FORCE_PACK_ID set to 0
 194   then pack_id ignored by read() and oldest readable fetched. */
 195#define SG_SET_FORCE_PACK_ID 0x227b
 196#define SG_GET_PACK_ID 0x227c /* Yields oldest readable pack_id (or -1) */
 197
 198#define SG_GET_NUM_WAITING 0x227d /* Number of commands awaiting read() */
 199
 200/* Yields max scatter gather tablesize allowed by current host adapter */
 201#define SG_GET_SG_TABLESIZE 0x227F  /* 0 implies can't do scatter gather */
 202
 203#define SG_GET_VERSION_NUM 0x2282 /* Example: version 2.1.34 yields 20134 */
 204
 205/* Returns -EBUSY if occupied. 3rd argument pointer to int (see next) */
 206#define SG_SCSI_RESET 0x2284
 207/* Associated values that can be given to SG_SCSI_RESET follow */
 208#define         SG_SCSI_RESET_NOTHING   0
 209#define         SG_SCSI_RESET_DEVICE    1
 210#define         SG_SCSI_RESET_BUS       2
 211#define         SG_SCSI_RESET_HOST      3
 212#define         SG_SCSI_RESET_TARGET    4
 213
 214/* synchronous SCSI command ioctl, (only in version 3 interface) */
 215#define SG_IO 0x2285   /* similar effect as write() followed by read() */
 216
 217#define SG_GET_REQUEST_TABLE 0x2286   /* yields table of active requests */
 218
 219/* How to treat EINTR during SG_IO ioctl(), only in SG 3.x series */
 220#define SG_SET_KEEP_ORPHAN 0x2287 /* 1 -> hold for read(), 0 -> drop (def) */
 221#define SG_GET_KEEP_ORPHAN 0x2288
 222
 223/* yields scsi midlevel's access_count for this SCSI device */
 224#define SG_GET_ACCESS_COUNT 0x2289  
 225
 226
 227#define SG_SCATTER_SZ (8 * 4096)
 228/* Largest size (in bytes) a single scatter-gather list element can have.
 229   The value used by the driver is 'max(SG_SCATTER_SZ, PAGE_SIZE)'.
 230   This value should be a power of 2 (and may be rounded up internally).
 231   If scatter-gather is not supported by adapter then this value is the
 232   largest data block that can be read/written by a single scsi command. */
 233
 234#define SG_DEFAULT_RETRIES 0
 235
 236/* Defaults, commented if they differ from original sg driver */
 237#define SG_DEF_FORCE_LOW_DMA 0  /* was 1 -> memory below 16MB on i386 */
 238#define SG_DEF_FORCE_PACK_ID 0
 239#define SG_DEF_KEEP_ORPHAN 0
 240#define SG_DEF_RESERVED_SIZE SG_SCATTER_SZ /* load time option */
 241
 242/* maximum outstanding requests, write() yields EDOM if exceeded */
 243#define SG_MAX_QUEUE 16
 244
 245#define SG_BIG_BUFF SG_DEF_RESERVED_SIZE    /* for backward compatibility */
 246
 247/* Alternate style type names, "..._t" variants preferred */
 248typedef struct sg_io_hdr Sg_io_hdr;
 249typedef struct sg_io_vec Sg_io_vec;
 250typedef struct sg_scsi_id Sg_scsi_id;
 251typedef struct sg_req_info Sg_req_info;
 252
 253
 254/* vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv */
 255/*   The older SG interface based on the 'sg_header' structure follows.   */
 256/* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ */
 257
 258#define SG_MAX_SENSE 16   /* this only applies to the sg_header interface */
 259
 260struct sg_header
 261{
 262    int pack_len;    /* [o] reply_len (ie useless), ignored as input */
 263    int reply_len;   /* [i] max length of expected reply (inc. sg_header) */
 264    int pack_id;     /* [io] id number of packet (use ints >= 0) */
 265    int result;      /* [o] 0==ok, else (+ve) Unix errno (best ignored) */
 266    unsigned int twelve_byte:1;
 267        /* [i] Force 12 byte command length for group 6 & 7 commands  */
 268    unsigned int target_status:5;   /* [o] scsi status from target */
 269    unsigned int host_status:8;     /* [o] host status (see "DID" codes) */
 270    unsigned int driver_status:8;   /* [o] driver status+suggestion */
 271    unsigned int other_flags:10;    /* unused */
 272    unsigned char sense_buffer[SG_MAX_SENSE]; /* [o] Output in 3 cases:
 273           when target_status is CHECK_CONDITION or
 274           when target_status is COMMAND_TERMINATED or
 275           when (driver_status & DRIVER_SENSE) is true. */
 276};      /* This structure is 36 bytes long on i386 */
 277
 278
 279/* IOCTLs: The following are not required (or ignored) when the sg_io_hdr_t
 280           interface is used. They are kept for backward compatibility with
 281           the original and version 2 drivers. */
 282
 283#define SG_SET_TIMEOUT 0x2201  /* unit: jiffies (10ms on i386) */
 284#define SG_GET_TIMEOUT 0x2202  /* yield timeout as _return_ value */
 285
 286/* Get/set command queuing state per fd (default is SG_DEF_COMMAND_Q.
 287   Each time a sg_io_hdr_t object is seen on this file descriptor, this
 288   command queuing flag is set on (overriding the previous setting). */
 289#define SG_GET_COMMAND_Q 0x2270   /* Yields 0 (queuing off) or 1 (on) */
 290#define SG_SET_COMMAND_Q 0x2271   /* Change queuing state with 0 or 1 */
 291
 292/* Turn on/off error sense trace (1 and 0 respectively, default is off).
 293   Try using: "# cat /proc/scsi/sg/debug" instead in the v3 driver */
 294#define SG_SET_DEBUG 0x227e    /* 0 -> turn off debug */
 295
 296#define SG_NEXT_CMD_LEN 0x2283  /* override SCSI command length with given
 297                   number on the next write() on this file descriptor */
 298
 299
 300/* Defaults, commented if they differ from original sg driver */
 301#ifdef __KERNEL__
 302#define SG_DEFAULT_TIMEOUT_USER (60*USER_HZ) /* HZ == 'jiffies in 1 second' */
 303#else
 304#define SG_DEFAULT_TIMEOUT      (60*HZ)      /* HZ == 'jiffies in 1 second' */
 305#endif
 306
 307#define SG_DEF_COMMAND_Q 0     /* command queuing is always on when
 308                                  the new interface is used */
 309#define SG_DEF_UNDERRUN_FLAG 0
 310
 311#endif
 312
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