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

       sd - Driver for SCSI Disk Drives

       #include <linux/hdreg.h>

       The  block device name has the following form: sdlp, where
       l is a letter denoting the physical drive, and p is a num-
       ber 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)  +  parti-
       tion_number, where drive_number is the number of the phys-
       ical drive in order of detection, and partition_number  is
       as follows:

       partition 0 is the whole drive
       partitions 1-4 are the DOS "primary" partitions
       partitions  5-8 are the DOS "extended" (or "logical") par-

       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 ioctl's are provided:

              Returns  the  BIOS disk parameters in the following
                     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 conve-
              nient 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 re-read of the SCSI disk partition tables.
              No parameter is needed.

              The scsi(4) ioctls  are  also  supported.   If  the
              ioctl(2)  parameter  is  required,  and it is NULL,
              then ioctl(2) will return -EINVAL.

       /dev/sd[a-h]: the whole device
       /dev/sd[a-h][0-8]: individual block partitions


                     Thu Dec 17 10:15:53 1992                   1