devio(4)devio(4)Namedevio - device information interface
Syntax
#include <sys/ioctl.h>
#include <sys/devio.h>
Description
The interface obtains status, device attributes, and other information
by polling the controlling device driver. There are two ioctl requests
associated with this interface: DEVIOCGET and DEVGETGEOM.
The file contains the needed structure and definitions to use the
DEVIOCGET and DEVGETGEOM ioctl requests.
The DEVIOCGET ioctl request is used to obtain generic device informa‐
tion by polling the underlying device driver. The following example
shows the basic structure used by this request:
/* 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 */
};
The 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 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.
The following example shows the basic structure used by this request:
/* 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;
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 This ioctl is used by the sub‐
routine to dynamically generate disktab entries.
dev_size This field contains the number of user accessible blocks on
the disk. The corresponding disktab field is which
describes the size of the "c" partition.
ntracks This field contains the number of tracks per cylinder and
corresponds to the field of a disktab entry.
nsectors This field contains the number of sectors per track and
corresponds to the field of a disktab entry.
ncylinders This field contains the number of cylinders on the disk and
corresponds to the field of a disktab entry.
attributes This field represents disk attributes.
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.
Restrictions
The DEVGETGEOM ioctl request is only supported on MSCP and SCSI disk
drivers.
See Alsocreatediskbyname(3x), ra(4), rz(4), disktab(5)devio(4)
