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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 follow-
       ing 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 con-
       nected  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 pre-
       vent their usage if you are not sure.

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

       l l.  Name Base minor # _ fdn  0

       5.25 inch double density device files:

       lw(1i) l l l l l.  Name Capac.    Cyl. Sect.     Heads     Base minor #
       _ fdnd360   360K 40   9    2    4

       5.25 inch high density device files:

       lw(1i) l l l l l.  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:

       lw(1i) l l l l l.  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:

       lw(1i) l l l l l.  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:

       lw(1i) l l l l l.  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  fol-
       lowing 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  for-
              mat.

       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  sec-
              tor.

       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 floppy-
       control.

NOTES
       The various formats allow to read and write many types of disks.   How-
       ever,  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  (AlainATlinux.lu),  David  Niemi  (niemidcATtux.org),  Bill
       Broadhurst (bbroadATnetcom.com).

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



Linux                             Jul 3, 1999                            FD(4)