devio.4

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 4 代码 · 共 126 行

.TH devio 4
.SH Name
devio \- device information interface
.SH Syntax
\fB#include <sys/ioctl.h>\fR
.br
\fB#include <sys/devio.h>\fR
.SH Description
.NXS "devio file" "device interface"
.NXR "device interface" 
The 
.PN devio 
interface obtains status, device attributes,
and other information by polling the controlling device driver.
There are two ioctl requests associated with this interface:
.RI DEVIOCGET
and 
.RI DEVGETGEOM.
.PP
The file 
.PN <sys/devio.h>
contains the needed structure and definitions to use the
.RI DEVIOCGET
and
.RI DEVGETGEOM
ioctl requests. 
.PP
The
.RI DEVIOCGET 
ioctl request is used to obtain generic device information by polling
the underlying device driver.  
The following example shows the basic structure used by this request: 
.EX 0
/* 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   slave_num;           /* Plug or line number        */
   char    dev_name[DEV_SIZE];  /* ULTRIX device mnemonic     */
   short   unit_num;            /* ULTRIX 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     */
};
.EE
.PP
The
.RI DEVGETGEOM
ioctl request is used to obtain disk geometry and attributes by polling
the underlying device driver.  This ioctl request is only supported on
MSCP and SCSI disk drivers.  The ioctl fails on other types of drivers
which do not support 
.RI DEVGETGEOM.  
The ioctl may 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.
.PP
The following example shows the basic structure used by this request:
.EX 0
/* Structure for DEVGETGEOM ioctl - disk geometry information */

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             */
   } geom_info;
   unsigned char       pad[124];  /* Allocate space for expansion */
} DEVGEOMST;
.EE
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
.PN /etc/disktab .
This ioctl is used by the 
.PN creatdiskbyname
subroutine to dynamically generate disktab entries.
.TP 12 
dev_size
This field contains the number of user accessible blocks on the disk.  
The corresponding disktab field is
.PN pc ,
which describes the size of the "c" partition.
.TP
ntracks
This field contains the number of tracks per cylinder and corresponds 
to the 
.PN nt
field of a disktab entry.
.TP
nsectors
This field contains the number of sectors per track and corresponds to 
the 
.PN ns
field of a disktab entry.
.TP
ncylinders
This field contains the number of cylinders on the disk 
and corresponds to the 
.PN nc
field of a disktab entry.
.TP
attributes
This field represents disk attributes.
.TP
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.
.SH Restrictions
The
.RI DEVGETGEOM
ioctl request is only supported on MSCP and SCSI disk drivers.
.SH See Also
creatediskbyname(3x), ra(4), rz(4), disktab(5)