SD(4)                      Linux Programmer's Manual                     SD(4)

       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:

              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.

              Returns the device size in sectors.  The ioctl(2) parameter
              should be a pointer to a long.

              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.

              the whole device

              individual block partitions

       This page is part of release 5.06 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                             2017-09-15                             SD(4)