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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	parti-
       tion_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") 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	conve-
	      nient operation of fdisk(1), efdisk(1), and lilo(1).  If the ge-
	      ometry  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 parame-
	      ter is needed.

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

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


				  1992-12-17				 SD(4)


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