devio(4)
Name
devio − device information interface
Syntax
#include <sys/ioctl.h>
#include <sys/devio.h>
Description
The devio 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 <sys/devio.h> contains the needed structure and definitions to use the DEVIOCGET and DEVGETGEOM ioctl requests.
The 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:
/* 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 /etc/disktab. This ioctl is used by the creatdiskbyname 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.
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.