FD(4)                     Special files                     FD(4)



NAME

       fd - floppy disk device


CONFIGURATION

       Floppy drives are block devices with major number 2.  Typ-
       ically 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 sup-
       ported by your drive, you may cause it mechanical  damage.
       Trying  once  if more tracks than the usual 40/80 are sup-
       ported 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:

       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  #  _
       fdnD360   360K 80   9    1    12



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FD(4)                     Special files                     FD(4)


       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:

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

       lw(1i)          l         l         l         l         l.
       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 re-enable autodetection,
              you have to issue an FDCLRPRM .

       FDGETDRVTYP
              returns the type of a drive (name parameter).   For



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FD(4)                     Special files                     FD(4)


              formats  which  work in several drive types, FDGET-
              DRVTYP 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 condi-
              tions.




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FD(4)                     Special files                     FD(4)


       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 floppycontrol.


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, 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  flop-
       pies which are formatted using GCR (group code recording),
       which is used by Apple II and  Macintosh  computers  (800k
       disks).   Reading  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.Knaff@imag.fr),    David    Niemi
       (niemidc@clark.net),  Bill Broadhurst (bbroad@netcom.com).


SEE ALSO

       floppycontrol(1), mknod(1), chown(1), getfdprm(1),  super-
       format(1), mount(8), setfdprm(8)



























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