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fd.4

FD

Section: Linux Programmer's Manual (4)
Updated: 1995-01-29
Index Return to Main Contents
 

NAME

fd - floppy disk device  

CONFIGURATION

Floppy drives are block devices with major number 2. Typically 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 supported by your drive, you may cause it mechanical damage. 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 prevent their usage if you are not sure.

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

NameBase minor #

fdn0

5.25 inch double density device files:

NameCapac.Cyl.Sect.HeadsBase minor #

fdnd360360K40924

5.25 inch high density device files:

NameCapac.Cyl.Sect.HeadsBase minor #

fdnh360360K409220
fdnh410410K4110248
fdnh420420K4210264
fdnh720720K809224
fdnh880880K8011280
fdnh12001200K801528
fdnh14401440K8018240
fdnh14761476K8218256
fdnh14941494K8318272
fdnh16001600K8020292

3.5 inch double density device files:

NameCapac.Cyl.Sect.HeadsBase minor #

fdnD360360K809112
fdnD720720K809216
fdnD800800K80102120
fdnD10401040K8013284
fdnD11201120K8014288

3.5 inch high density device files:

NameCapac.Cyl.Sect.HeadsBase minor #

fdnH360360K409212
fdnH720720K809216
fdnH820820K8210252
fdnH830830K8310268
fdnH14401440K8018228
fdnH16001600K80202124
fdnH16801680K8021244
fdnH17221722K8221260
fdnH17431743K8321276
fdnH17601760K8022296
fdnH18401840K80232116
fdnH19201920K80242100

3.5 inch extra density device files:

NameCapac.Cyl.Sect.HeadsBase minor #

fdnE28802880K8036232
fdnCompaQ2880K8036236
fdnE32003200K80402104
fdnE35203520K80442108
fdnE38403840K80482112
 

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 formats which work in several drive types, FDGETDRVTYP 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 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 floppycontrol.  

FILES

/dev/fd*  

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 floppies 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.  

SEE ALSO

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

COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
CONFIGURATION
DESCRIPTION
FILES
NOTES
SEE ALSO
COLOPHON

 

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