FD(4)                     Special files                     FD(4)

       fd - floppy disk device

       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:

       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

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

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

              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, FDGET-
              DRVTYP returns a name which is appropriate for  the
              oldest drive type which supports this format.

              invalidates the buffer cache for the given drive.

              sets  the  error  thresholds  for reporting errors,
              aborting the operation,  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 (almost)
              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 together.

              sets various drive parameters.

              reads these parameters back.

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

              polls the drive and return its state.

              gets the floppy controller state.

              resets  the  floppy controller under certain condi-

              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.

       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.


       Alain    Knaff    (Alain.Knaff@imag.fr),    David    Niemi
       (niemidc@clark.net),  Bill Broadhurst (bbroad@netcom.com).

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

Linux                    January 29, 1995                       1