fd(4)									 fd(4)

Name
       fd - Floppy disk interface

Syntax
       device	       fd0	  at ibus?     vector fdintr

Description
       The driver is for used with Digital's non-scsi floppy disk drives.

       If  the minor number is less than 64, the driver select number is indi‐
       cated by bits 4 and 5, and the partition by bits 0 through 3.   If  the
       minor  number  is  one of 64, 65, 66, or 67, the drive select number is
       indicated by bits 0 and 1, and disk partitions are  disabled.   In  the
       latter  case,  the  entire surface of the media is treated as one large
       partition, and attempts to change the partition table will  fail.   The
       major  number is 48 for the block interface and 83 for the raw (charac‐
       ter) interface.

       The device names are of the format { rfd<n> | [r]fd<n><p> }, where  <n>
       indicates  the drive select number using one of the characters 0, 1, 2,
       or 3; <p> indicates the partition using one of the characters a through
       h;  rfd	indicates the raw interface; and fd indicates the block inter‐
       face.  If p is absent, partitioning is disabled.

       The block interface is  restricted  to  512-byte,  disk-sector  aligned
       accesses.   Reads  or  writes  that attempt to start at the middle of a
       sector actually start at the beginning of the sector.

       There is no sector-boundary limitation when using the raw interface.

       The driver protects the process that has opened the floppy disk	device
       from  an	 accidental media change by preventing access to the device if
       the media is removed and reinserted.  To access	the  drive  after  the
       media  has been changed, either the device must be closed and reopened,
       or a DEVIOCGET or FDIOTPRRST ioctl must be issued.   You	 can  use  the
       command and its option to issue the FDIOTPRRST ioctl.

       When a floppy disk device is first opened after changing media, a delay
       occurs while the partition table is read from the media if  the	device
       is not of type rfd<n>.  If the device is opened with FNDELAY, partition
       table reading may be delayed until  the	first  actual  read  or	 write
       request.

       When  accessing	media  containing non-UFS data, the data on that media
       may appear to be a valid partition table.  In this case, the user  will
       probably	 not be able to access the media.  To work around the problem,
       use the rfd<n> device.

       Partitions a and c begin at physical sector 0  and  occupy  the	entire
       disk.  All other partitions also begin at physical sector 0, but are of
       length zero.  You can change partition sizes by using the command.

       The currently supported disk drive is the RX26.

       The supported media types in the RX26 are  the  350DD  of  size	737280
       (1440 sectors), 350HD of size 1474560 (2880 sectors), and 350ED of size
       2949120 (5760 sectors).

   Ioctl Support
       Several special ioctls are defined for use with the device driver.  Use
       of these requires that and be included.	See the file for reference.

       FDIOSENSE  returns information about the current state of the drive via
       the structure fd_sense.	All elements of this structure are initialized
       by this call.  See comments in for use of each element.

       FDIOGETMTYP  returns information about the media currently in the drive
       via the structure fd_mt.	 All elements of this structure	 are  initial‐
       ized by this call.  See comments in for use of each element.

       FDIOFMTDSK, FDIOFFBSETUP, FDIOFFBNEXT, and FDIOFMTTRK are used for disk
       formatting.  Data is passed to and from these calls  via	 certain  ele‐
       ments  of  a structure of type fd_fmt_spec.  See comments in for use of
       each element.  FDIOFMTDSK causes	 the  entire  disk  to	be  formatted.
       FDIOFMTTRK  causes  a specified track to be formatted.  The combination
       of FDIOFFBSETUP and FDIOFFBNEXT cause the entire disk to be  formatted,
       a  little at a time, allowing the calling process to display an updated
       status line indicating the progress of the format.

       FDIOTPRRST causes the driver to ignore the fact that  the  media	 might
       have  just been removed and reinserted.	Status information is returned
       via a fd_sense structure, just as with the FDIOSENSE call.

       FDIOSEEK allows the user to specify the position of  the	 next  single-
       sector  access  (and  only  the next access) in any of several formats.
       These formats include  logical-sector-number  format,  physical-sector-
       number  format,	and  cylinder-head-sector  format.   These formats are
       specified in a structure of type fd_seek.  See comments in for  use  of
       each element.

       FDIOMKCHS  and  FDIOMKPSN  are used to translate between cylinder-head-
       sector sector specification and physical-sector-number sector  specifi‐
       cation.	Data is passed to and from these calls via certain elements of
       a structure of type fd_chs_psn.	See comments in for use of  each  ele‐
       ment.

       The  calls  DEVIOCGET,  DEVGETGEOM, DIOCGETPT, DIOCDGTPT, and DIOCSETPT
       are also supported and perform in their expected	 manner.   A  call  to
       DEVIOCGET also has the effect of calling FDIOTPRRST.

Files
See Also
       nbuf(4), fddisk[8], dkio(4), chpt(8), MAKEDEV(8), uerf(8)

									 fd(4)

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