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devio

Section: Environments, Tables, and Troff Macros (7)
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NAME

devio - device information interface  

SYNOPSIS

#include <sys/ioctl.h>
#include <sys/devgetinfo.h>
#include <sys/devio.h>  

DESCRIPTION

The devio interface obtains status, device attributes, and other information by polling the controlling device driver. There are three ioctl requests associated with this interface: DEVIOCGET, DEVGETINFO and DEVGETGEOM.

The file <sys/devgetinfo.h> contains the structures and definitions needed by the DEVGETINFO ioctl request; the file <sys/devio.h> contains the structures and definitions needed by the DEVIOCGET and DEVGETGEOM ioctl requests.

The DEVGETINFO and DEVIOCGET ioctl requests are used to obtain generic device information by polling the underlying device driver. DEVGETINFO is used by disk and tape device drivers; DEVIOCGET is used by other kernel subsystems.

For DEVIOCGET, the devget structure is the basic structured used by this request. The devget structure has the following definition:

/* Structure for DEVIOCGET ioctl - device get status command */

struct devget {
   short   category;            /* Category                   */
   short   bus;                 /* Bus                        */
   char    interface[DEV_SIZE]; /* Interface (string)         */
   char    device[DEV_SIZE];    /* Device (string)            */
   short   adpt_num;            /* Adapter number             */
   short   nexus_num;           /* Nexus or node on adapter # */
   short   bus_num;             /* Bus number                 */
   short   ctlr_num;            /* Controller number          */
   short   rctlr_num;           /* Remote controller number   */
   short   slave_num;           /* Plug or line number        */
   char    dev_name[DEV_SIZE];  /* Device mnemonic            */
   short   unit_num;            /* Device unit number         */
   unsigned soft_count;         /* Driver soft error count    */
   unsigned hard_count;         /* Driver hard error count    */
   long    stat;                /* Generic status mask        */
   long    category_stat;       /* Category specific mask     */ };

For DEVGETINFO, the device_info_t union is the top-level definition of the information returned to the device_info_t union is the top-level definition of the information returned to the DEVGETINFO ioctl request. It has the following definition:

typedef union device_info {
    int version;          /* version number             */
    v1_device_info_t v1;  /* bus and device information */
    uchar_t pad[1024];    /* unused                     */ } device_info_t;

The v1_device_info_t structure contains all the information returned to the user data buffer by the DEVGETINFO ioctl command. This structure is contained within the device_info_t structure so that the same interface can be used for various versions of the data structure. It has the following definition:

typedef struct v1_device_info {
    int version;                    /* version number               */
    short category;                 /* device type, i.e., disk      */
    short bus;                      /* bus type                     */
    char interface[DEV_STRING_SIZE]; /* interface type, i.e., HSC40 */
    char device[DEV_STRING_SIZE];   /* device description           */
    char dev_name[DEV_STRING_SIZE]; /* device name                  */
    ulong_t soft_count;             /* number of soft errors        */
    ulong_t hard_count;             /* number of hard errors        */
    v1_devtype_info_t devinfo;      /* device-type information      */
    v1_bustype_info_t businfo;      /* bus-type information         */
     uchar_t private[DEV_PRIVATE_LEN]; /* driver-specific           */ } v1_device_info_t;

The v1_bustype_info_t structure returns information about the bus type. It has the following definition: typedef struct v1_bustype_info {
    int adpt_num;  /* controller chip relative to current adaptor */
    int nexus_num; /* slot that the adaptor is using              */
    int bus_num;   /* logical bus number for the adaptor          */
    int ctlr_num;  /* system-wide instance number of the adaptor  */
    int rctlr_num; /* remote ID for the adaptor                   */
    int slave_num; /* number of the device relative to the                  controlling hardware */

    int unit_num;  /* system-wide number of this device           */
    int pad0;      /* unused                                      */
    union {          v1_scsi_bus_info_t scsi; /* SCSI-specific */
         uchar_t busdata[DEV_BUS_LEN]; /* bus-specific */

    } bus; } v1_bustype_info_t;

The v1_devtype_info_t union returns device-specific information. The contents of the v1_devtype_info_t union depends on the device type, either disk, tape, or other device type. The structure has the following definition:

typedef union v1_devtype_info {
    v1_disk_dev_info_t disk;       /* disk-specific status        */
    v1_tape_dev_info_t tape;       /* tape-specific status        */
    uchar_t devdata[DEV_TYPE_LEN]; /* other device-type status    */ } v1_devtype_info_t;

For disk devices, the v1_devtype_info_t union contains a v1_disk_dev_info_t structure, defined as follows:

typedef struct v1_disk_dev_info {
    ulong_t  status;           /* device status                      */
    ulong_t  capacity;         /* number of blocks on the device     */
    ulong_t  blocksz;          /* number of bytes per block          */
    uchar_t  class;            /* disk class, such as diskette       */
    uchar_t  part_num;         /* total number of partitions         */
    uchar_t  raid_level        /* RAID level of the device           */
    uchar_t  pad0;             /* unused                             */
    ushort_t media_changes;    /* number of media changes (diskette) */
    ushort_t pad1;             /* unused                             */
    union {
        struct {          uchar_t density_code; /* SCSI density code */
         uchar_t flags; /* SCSI flags */

        } scsi;         uchar_t archdata[DEV_ARCH_LEN]; /* architecture-specific */

    } arch; } v1_disk_dev_info_t;

For tape devices, the v1_devtype_info_t union contains a v1_tape_dev_info_t structure, defined as follows:

typedef struct v1_tape_dev_info {
    uint_t  media_status;          /* current status of the media    */
    uint_t  unit_status;           /* current status of the unit     */
    long    recordsz;              /* record size, or 0 for
                                      variable-sized records         */
    long    density_bpi;           /* current density setting        */
    long    density_bpi_wrt;       /* density used for writes        */
    long    position;              /* number of records written since
                                      the last file mark             */
    long    fm_cnt;                /* number of file marks since the
                                      beginning of the tape          */
    uchar_t class;                 /* tape device class              */
    uchar_t pad[7];                /* unused                         */
    union {
        struct {          uint_t blocking_factor; /* blocking factor */
         uchar_t valid_flags; /* valid flags */
         uchar_t density_code; /* density code */
         uchar_t buffered_mode; /* buffered mode */
         uchar_t speed; /* tape speed */
         uchar_t compression_code; /* compression code */

        } scsi;         uchar_t archdata[DEV_ARCH_LEN]; /* architecture-specific */

    } arch; } v1_tape_dev_info_t;

The DEVGETGEOM ioctl request is used to obtain disk geometry and attributes by polling the underlying device driver. The ioctl fails on other types of drivers which do not support DEVGETGEOM. The DEVGETGEOM may also fail if the device driver is unable to obtain geometry information. This could happen if the disk media is removable and there is no media loaded in the drive.

The following example shows the basic structure used by this request:

typedef union devgeom {
  struct {
     unsigned long  dev_size;   /* number of blocks in user area    */
     unsigned short  ntracks;   /* number of tracks per cylinder    */
     unsigned short  nsectors;  /* number of sectors per track      */
     unsigned short  ncylinders; /* total number of cylinders       */
     unsigned long   attributes; /* device attributes               */
     unsigned long sector_size;  /* number of bytes per sector      */
     unsigned long min_trans;    /* minimum transer size            */
     unsigned long max_trans;    /* maximum transfer size           */
     unsigned long prefer_trans; /* perferred transfer size         */
     unsigned int    headswitch; /* head switch time                */
     unsigned int    trkseek;    /* track-to-track seek time        */
     unsigned int    acylinders; /* alternate cylinders per unit    */
     unsigned short  rpm;        /* rotational speed                */
     unsigned short  interleave; /* hardware sector interleave      */
     unsigned short  trackskew;  /* sector 0 skew, per track        */
     unsigned short  sparespertrack; /* spare sectors per track     */
     unsigned short  sparespercyl;   /* spare sectors per cylinder  */
     unsigned short  cylskew;    /* sector 0 skew, per cylinder     */
   } geom_info;
   unsigned char       pad[108];  /* Allocate space for expansion */ } DEVGEOMST;

The following is a description of the fields of the DEVGEOMST data structure. Many of the fields correspond to attributes that are often specified in the disk description file /etc/disktab . This ioctl is used by the creatediskbyname subroutine to dynamically generate disktab entries.

dev_size
This field contains the number of user accessible blocks on the disk. The corresponding disktab field is pc, which describes the size of the "c" partition.
ntracks
This field contains the number of tracks per cylinder and corresponds to the nt field of a disktab entry.
nsectors
This field contains the number of sectors per track and corresponds to the ns field of a disktab entry.
ncylinders
This field contains the number of cylinders on the disk and corresponds to the nc field of a disktab entry.
attributes
This field represents disk attributes.
sector_size
This field specifies the number of bytes per sector.
min_trans
This field specifies the minimum number of bytes that can be transferred at one time.
max_trans
This field specifies the maximum number of bytes that can be transferred at one time.
prefer_trans
This field specifies the preferred number of bytes in any single transfer.
headswitch
This field specifies the number of microseconds the disk takes to switch heads.
trkseek
This field specifies the number of microseconds the disk takes to seek from track to track.
acylinders
This field specifies the number of alternate cylinders that exist on the unit.
rpm
This field specifies the rotational speed of the disk.
interleave
This field specifies the hardware sector interleave.
trackskew
This field specifies the sector 0 skew, per track.
sparespertrack
This field specifies the number of spare sectors that exist on each track.
sparespercyl
This field specifies the number of spare sectors that exist on each cynlinder.
cylskew
This field specifies the sector 0 skew, per cylinder.
pad
This field is not used to store disk information. The pad element of the DEVGEOMST is used to provide room for future expansion of the information fields.
 

RELATED INFORMATION

disktab(4) delim off


 

Index

NAME
SYNOPSIS
DESCRIPTION
RELATED INFORMATION

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Time: 02:40:26 GMT, October 02, 2010