sd - driver for SCSI disk drives
#include <linux/hdreg.h> /* for HDIO_GETGEO */
#include <linux/fs.h> /* for BLKGETSIZE and BLKRRPART */
The block device name has the following form:
sdlp, where
l
is a letter denoting the physical drive, and
p is a number denoting the
partition on that physical drive. Often, the partition number,
p, will
be left off when the device corresponds to the whole drive.
SCSI disks have a major device number of 8, and a minor device number of the
form (16 *
drive_number) +
partition_number, where
drive_number is the number of the physical drive in order of detection,
and
partition_number is as follows:
- +3
- partition 0 is the whole drive
- partitions 1–4 are the DOS "primary" partitions
- partitions 5–8 are the DOS "extended" (or
"logical") partitions
For example,
/dev/sda will have major 8, minor 0, and will refer to all
of the first SCSI drive in the system; and
/dev/sdb3 will have major 8,
minor 19, and will refer to the third DOS "primary" partition on the
second SCSI drive in the system.
At this time, only block devices are provided. Raw devices have not yet been
implemented.
The following
ioctls are provided:
- HDIO_GETGEO
- Returns the BIOS disk parameters in the following structure:
struct hd_geometry {
unsigned char heads;
unsigned char sectors;
unsigned short cylinders;
unsigned long start;
};
- A pointer to this structure is passed as the ioctl(2)
parameter.
- The information returned in the parameter is the disk geometry of the
drive as understood by DOS! This geometry is not the
physical geometry of the drive. It is used when constructing the drive's
partition table, however, and is needed for convenient operation of
fdisk(1), efdisk(1), and lilo(1). If the geometry
information is not available, zero will be returned for all of the
parameters.
- BLKGETSIZE
- Returns the device size in sectors. The ioctl(2) parameter should
be a pointer to a long.
- BLKRRPART
- Forces a reread of the SCSI disk partition tables. No parameter is
needed.
- The SCSI ioctl(2) operations are also supported. If the
ioctl(2) parameter is required, and it is NULL, then
ioctl(2) fails with the error EINVAL.
- /dev/sd[a-h]
- the whole device
- /dev/sd[a-h][0-8]
- individual block partitions