sg.h

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    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 * 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 1

/* 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 */
#define SG_DEFAULT_TIMEOUT (60*HZ) /* HZ == 'jiffies in 1 second' */
#define SG_DEF_COMMAND_Q 0     /* command queuing is always on when
				  the new interface is used */
#define SG_DEF_UNDERRUN_FLAG 0

#endif