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

NAME

       fd - floppy disk device

CONFIGURATION

       Floppy  drives  are  block  devices  with major number 2.  Typically they are owned by root.floppy (i.e., user root, group floppy) and have
       either mode 0660 (access checking via group membership) or mode 0666 (everybody has access).  The minor numbers	encode	the  device  type,
       drive  number, and controller number.  For each device type (that is, combination of density and track count) there is a base minor number.
       To this base number, add the drive's number on its controller and 128 if the drive is on the secondary controller.  In the following device
       tables, n represents the drive number.

       Warning:  If you use formats with more tracks than supported by your drive, you may cause it mechanical damage.	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 #
       ----------------------------------------------------------
       fdnD360	    360K     80     9	    1	    12
       fdnD720	    720K     80     9	    2	    16
       fdnD800	    800K     80     10	    2	    120
       fdnD1040     1040K    80     13	    2	    84
       fdnD1120     1120K    80     14	    2	    88

       3.5 inch high density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnH360	    360K     40     9	    2	    12
       fdnH720	    720K     80     9	    2	    16
       fdnH820	    820K     82     10	    2	    52
       fdnH830	    830K     83     10	    2	    68
       fdnH1440     1440K    80     18	    2	    28
       fdnH1600     1600K    80     20	    2	    124

       fdnH1680     1680K    80     21	    2	    44
       fdnH1722     1722K    82     21	    2	    60
       fdnH1743     1743K    83     21	    2	    76
       fdnH1760     1760K    80     22	    2	    96
       fdnH1840     1840K    80     23	    2	    116
       fdnH1920     1920K    80     24	    2	    100

       3.5 inch extra density device files:

       Name	    Capac.   Cyl.   Sect.   Heads   Base minor #
       ----------------------------------------------------------
       fdnE2880     2880K    80     36	    2	    32
       fdnCompaQ    2880K    80     36	    2	    36
       fdnE3200     3200K    80     40	    2	    104
       fdnE3520     3520K    80     44	    2	    108
       fdnE3840     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 reenable 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.

FILES

       /dev/fd*

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.

SEE ALSO

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

COLOPHON

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    1995-01-29								     FD(4)