1FD(4) Linux Programmer's Manual FD(4)
2
6 fd - floppy disk device
7
9 Floppy drives are block devices with major number 2. Typically they
10 are owned by root.floppy (i.e., user root, group floppy) and have
11 either mode 0660 (access checking via group membership) or mode 0666
12 (everybody has access). The minor numbers encode the device type, drive
13 number, and controller number. For each device type (that is, combina‐
14 tion of density and track count) there is a base minor number. To this
15 base number, add the drive's number on its controller and 128 if the
16 drive is on the secondary controller. In the following device tables, n
17 represents the drive number.
18 Warning: If you use formats with more tracks than supported by your
20 drive, you may cause it mechanical damage. Trying once if more tracks
21 than the usual 40/80 are supported should not damage it, but no war‐
22 ranty is given for that. Don't create device entries for those formats
23 to prevent their usage if you are not sure.
24 Drive independent device files which automatically detect the media
26 format and capacity:
27 Name Base minor #
29 ────────────────────
30 fdn 0
31 5.25 inch double density device files:
33 Name Capac. Cyl. Sect. Heads Base minor #
35 ──────────────────────────────────────────────────────────
36 fdnd360 360K 40 9 2 4
37 5.25 inch high density device files:
39 Name Capac. Cyl. Sect. Heads Base minor #
41 ──────────────────────────────────────────────────────────
42 fdnh360 360K 40 9 2 20
43 fdnh410 410K 41 10 2 48
44 fdnh420 420K 42 10 2 64
45 fdnh720 720K 80 9 2 24
46 fdnh880 880K 80 11 2 80
47 fdnh1200 1200K 80 15 2 8
48 fdnh1440 1440K 80 18 2 40
49 fdnh1476 1476K 82 18 2 56
50 fdnh1494 1494K 83 18 2 72
51 fdnh1600 1600K 80 20 2 92
52 3.5 inch double density device files:
54 Name Capac. Cyl. Sect. Heads Base minor #
56 ──────────────────────────────────────────────────────────
57 fdnD360 360K 80 9 1 12
58 fdnD720 720K 80 9 2 16
59 fdnD800 800K 80 10 2 120
60 fdnD1040 1040K 80 13 2 84
61 fdnD1120 1120K 80 14 2 88
62 3.5 inch high density device files:
64 Name Capac. Cyl. Sect. Heads Base minor #
66 ──────────────────────────────────────────────────────────
67 fdnH360 360K 40 9 2 12
68 fdnH720 720K 80 9 2 16
69 fdnH820 820K 82 10 2 52
70 fdnH830 830K 83 10 2 68
71 fdnH1440 1440K 80 18 2 28
72 fdnH1600 1600K 80 20 2 124
73 fdnH1680 1680K 80 21 2 44
74 fdnH1722 1722K 82 21 2 60
75 fdnH1743 1743K 83 21 2 76
76 fdnH1760 1760K 80 22 2 96
77 fdnH1840 1840K 80 23 2 116
78 fdnH1920 1920K 80 24 2 100
79 3.5 inch extra density device files:
81 Name Capac. Cyl. Sect. Heads Base minor #
83 ──────────────────────────────────────────────────────────
84 fdnE2880 2880K 80 36 2 32
85 fdnCompaQ 2880K 80 36 2 36
86 fdnE3200 3200K 80 40 2 104
87 fdnE3520 3520K 80 44 2 108
88 fdnE3840 3840K 80 48 2 112
89
91 fd special files access the floppy disk drives in raw mode. The fol‐
92 lowing ioctl(2) calls are supported by fd devices:
93 FDCLRPRM
95 clears the media information of a drive (geometry of disk in
96 drive).
97 FDSETPRM
99 sets the media information of a drive. The media information
100 will be lost when the media is changed.
101 FDDEFPRM
103 sets the media information of a drive (geometry of disk in
104 drive). The media information will not be lost when the media is
105 changed. This will disable autodetection. In order to re-enable
106 autodetection, you have to issue an FDCLRPRM.
107 FDGETDRVTYP
109 returns the type of a drive (name parameter). For formats which
110 work in several drive types, FDGETDRVTYP returns a name which is
111 appropriate for the oldest drive type which supports this for‐
112 mat.
113 FDFLUSH
115 invalidates the buffer cache for the given drive.
116 FDSETMAXERRS
118 sets the error thresholds for reporting errors, aborting the
119 operation, recalibrating, resetting, and reading sector by sec‐
120 tor.
121 FDSETMAXERRS
123 gets the current error thresholds.
124 FDGETDRVTYP
126 gets the internal name of the drive.
127 FDWERRORCLR
129 clears the write error statistics.
130 FDWERRORGET
132 reads the write error statistics. These include the total number
133 of write errors, the location and disk of the first write error,
134 and the location and disk of the last write error. Disks are
135 identified by a generation number which is incremented at
136 (almost) each disk change.
137 FDTWADDLE
139 Switch the drive motor off for a few microseconds. This might be
140 needed in order to access a disk whose sectors are too close
141 together.
142 FDSETDRVPRM
144 sets various drive parameters.
145 FDGETDRVPRM
147 reads these parameters back.
148 FDGETDRVSTAT
150 gets the cached drive state (disk changed, write protected et
151 al.)
152 FDPOLLDRVSTAT
154 polls the drive and return its state.
155 FDGETFDCSTAT
157 gets the floppy controller state.
158 FDRESET
160 resets the floppy controller under certain conditions.
161 FDRAWCMD
163 sends a raw command to the floppy controller.
164 For more precise information, consult also the <linux/fd.h> and
166 <linux/fdreg.h> include files, as well as the manual page for floppy‐
167 control.
168
170 The various formats allow to read and write many types of disks. How‐
171 ever, if a floppy is formatted with a too small inter sector gap, per‐
172 formance may drop, up to needing a few seconds to access an entire
173 track. To prevent this, use interleaved formats. It is not possible to
174 read floppies which are formatted using GCR (group code recording),
175 which is used by Apple II and Macintosh computers (800k disks). Read‐
176 ing floppies which are hard sectored (one hole per sector, with the
177 index hole being a little skewed) is not supported. This used to be
178 common with older 8 inch floppies.
179
181 /dev/fd*
182
184 Alain Knaff (Alain.Knaff@imag.fr), David Niemi (niemidc@clark.net),
185 Bill Broadhurst (bbroad@netcom.com).
186
188 chown(1), floppycontrol(1), getfdprm(1), mknod(1), superformat(1),
189 mount(8), setfdprm(8)
190Special files 1995-01-29 FD(4)