fd (4)

Leading comments

{{{}}}
{{{  Notes
 Copyright (c) 1993 Michael Haardt (michael@moria.de)
 and 1994,1995, 1997 Alain Knaff (alain@linux.lu)

 This is free documentation; you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation; either version 2 of
 the License, or (at your option) any later version.

 The GNU General Public License's references to "object code"
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 documen...

(The comments found at the beginning of the groff file "man4/fd.4".)

NAME

fd - floppy disk device

CONFIGURATION

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 following 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 connected 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 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 #
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

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.

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.

FILES

/dev/fd*

AUTHORS

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

SEE ALSO

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