FD(4)                            Special files                           FD(4)

       fd - floppy disk device

       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:

       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

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

              clears the media information of a drive  (geometry  of  disk  in

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

              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 .

              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-

              invalidates the buffer cache for the given drive.

              sets the error thresholds for reporting errors, aborting the op-
              eration, recalibrating, resetting, and reading sector by sector.

              gets the current error thresholds.

              gets the internal name of the drive.

              clears the write error statistics.

              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  (al-
              most) each disk change.

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

              sets various drive parameters.

              reads these parameters back.

              gets  the  cached  drive state (disk changed, write protected et

              polls the drive and return its state.

              gets the floppy controller state.

              resets the floppy controller under certain conditions.

              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-

       The various formats allow one to read and write many  types  of  disks.
       However,  if  a  floppy is formatted with a too small inter sector gap,
       performance 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 in-
       dex hole being a little skewed) is not supported.  This used to be com-
       mon with older 8 inch floppies.


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

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

Linux                             Jul 3, 1999                            FD(4)
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