FD(4)								   Special files							     FD(4)

NAME

       fd - floppy disk device

CONFIGURATION

       Floppy  drives  are  block devices with major number 2.	Typically they are owned by root.floppy and have either mode 0660 (access checking
       via group membership) or mode 0666 (everybody has access).  For the following devices, n is the drive number.  It is 0 for the first drive,
       1 for the second etc.  To get a minor number for a specific drive connected to the first controller, add n to the minor base number.  If it
       is connected to the second controller, add n+128 to the minor base number.  Warning: If you use formats with more tracks than supported	by
       your  drive,  you  may  damage it mechanically.	Trying once if more tracks than the usual 40/80 are supported should not damage it, but no
       warranty is given for that.  Don't create device entries for those formats to prevent their usage if you are not sure.

       Drive independent device files which automatically detect the media format and capacity:

       Name   Base minor #
       --------------------
       fdn    0

       5.25 inch double density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnd360	    360K     40     9	    2	    4

       5.25 inch high density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnh360	    360K     40     9	    2	    20
       fdnh410	    410K     41     10	    2	    48
       fdnh420	    420K     42     10	    2	    64
       fdnh720	    720K     80     9	    2	    24
       fdnh880	    880K     80     11	    2	    80
       fdnh1200     1200K    80     15	    2	    8
       fdnh1440     1440K    80     18	    2	    40
       fdnh1476     1476K    82     18	    2	    56
       fdnh1494     1494K    83     18	    2	    72
       fdnh1600     1600K    80     20	    2	    92

       3.5 inch double density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnu360	    360K     80     9	    1	    12
       fdnu720	    720K     80     9	    2	    16
       fdnu800	    800K     80     10	    2	    120
       fdnu1040     1040K    80     13	    2	    84
       fdnu1120     1120K    80     14	    2	    88

       3.5 inch high density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnu360	    360K     40     9	    2	    12
       fdnu720	    720K     80     9	    2	    16
       fdnu820	    820K     82     10	    2	    52
       fdnu830	    830K     83     10	    2	    68
       fdnu1440     1440K    80     18	    2	    28
       fdnu1600     1600K    80     20	    2	    124
       fdnu1680     1680K    80     21	    2	    44
       fdnu1722     1722K    82     21	    2	    60
       fdnu1743     1743K    83     21	    2	    76

       fdnu1760     1760K    80     22	    2	    96
       fdnu1840     1840K    80     23	    2	    116
       fdnu1920     1920K    80     24	    2	    100

       3.5 inch extra density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnu2880     2880K    80     36	    2	    32
       fdnu3200     3200K    80     40	    2	    104
       fdnu3520     3520K    80     44	    2	    108
       fdnu3840     3840K    80     48	    2	    112

DESCRIPTION

       fd special files access the floppy disk drives in raw mode.  The following ioctl(2) calls are supported by fd devices:

       FDCLRPRM
	      clears the media information of a drive (geometry of disk in drive).

       FDSETPRM
	      sets the media information of a drive. The media information will be lost when the media is changed.

       FDDEFPRM
	      sets the media information of a drive (geometry of disk in drive). The media information will not be lost when the media is changed.
	      This will disable autodetection. In order to re-enable autodetection, you have to issue an FDCLRPRM .

       FDGETDRVTYP
	      returns  the  type  of a drive (name parameter).	For formats which work in several drive types, FDGETDRVTYP returns a name which is
	      appropriate for the oldest drive type which supports this format.

       FDFLUSH
	      invalidates the buffer cache for the given drive.

       FDSETMAXERRS
	      sets the error thresholds for reporting errors, aborting the operation, recalibrating, resetting, and reading sector by sector.

       FDSETMAXERRS
	      gets the current error thresholds.

       FDGETDRVTYP
	      gets the internal name of the drive.

       FDWERRORCLR
	      clears the write error statistics.

       FDWERRORGET
	      reads the write error statistics. These include the total number of write errors, the location and disk of the  first  write  error,
	      and the location and disk of the last write error. Disks are identified by a generation number which is incremented at (almost) each
	      disk change.

       FDTWADDLE
	      Switch the drive motor off for a few microseconds. This might be needed in order to access  a  disk  whose  sectors  are	too  close
	      together.

       FDSETDRVPRM
	      sets various drive parameters.

       FDGETDRVPRM
	      reads these parameters back.

       FDGETDRVSTAT
	      gets the cached drive state (disk changed, write protected et al.)

       FDPOLLDRVSTAT
	      polls the drive and return its state.

       FDGETFDCSTAT
	      gets the floppy controller state.

       FDRESET
	      resets the floppy controller under certain conditions.

       FDRAWCMD
	      sends a raw command to the floppy controller.

       For  more  precise  information, consult also the <linux/fd.h> and <linux/fdreg.h> include files, as well as the manual page for floppycon-
       trol.

NOTES

       The various formats allow to read and write many types of disks.  However, if a floppy is formatted with a too small inter sector gap, per-
       formance  may  drop, up to needing a few seconds to access an entire track. To prevent this, use interleaved formats. It is not possible to
       read floppies which are formatted using GCR (group code recording), which is used by Apple II and Macintosh computers (800k disks).   Read-
       ing  floppies  which  are hard sectored (one hole per sector, with the index hole being a little skewed) is not supported.  This used to be
       common with older 8 inch floppies.

FILES

       /dev/fd*

AUTHORS

       Alain Knaff (Alain@linux.lu), David Niemi (niemidc@tux.org), Bill Broadhurst (bbroad@netcom.com).

SEE ALSO

       floppycontrol(1), mknod(1), chown(1), getfdprm(1), superformat(1), mount(8), setfdprm(1)

Linux								    Jul 3, 1999 							     FD(4)