2 .\" Copyright (c) 1994 Wilko Bulte
3 .\" Copyright (c) 2001 Joerg Wunsch
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35 .Nd "PC architecture floppy disk controller driver"
40 .Pa /boot/device.hints :
41 .Cd hint.fdc.0.at="isa"
42 .Cd hint.fdc.0.port="0x3F0"
43 .Cd hint.fdc.0.irq="6"
44 .Cd hint.fdc.0.drq="2"
45 .Cd hint.fdc.0.flags="0x0"
46 .Cd hint.fd.0.at="fdc0"
47 .Cd hint.fd.0.drive="0"
48 .Cd hint.fd.0.flags="0x0"
49 .Cd hint.fd.1.at="fdc0"
50 .Cd hint.fd.1.drive="1"
51 .Cd hint.fd.1.flags="0x0"
54 This driver provides access to floppy disk drives.
56 either FM (single-density) or MFM (double or high-density) recording
59 Floppy disk controllers can connect up to four drives each.
62 driver can currently handle up to two drives per controller (or four
65 driver initialization, an attempt is made to find out the type of the
66 floppy controller in use.
67 The known controller types are either the
68 original NE765 or i8272 chips, or alternatively
70 controllers that are compatible with the NE72065 or i82077 chips.
71 These enhanced controllers (among other enhancements) implement a FIFO
72 for floppy data transfers that will automatically be enabled once an
73 enhanced chip has been detected.
74 This FIFO activation can be disabled
75 using the per-controller flags value of
78 By default, this driver creates a single device node
80 for each attached drive with number
82 For historical reasons, device nodes that use a trailing UFS-style
83 partition letter (ranging from
87 can also be accessed, which will be implemented as symbolic links to
90 Accessing the main device node will attempt to autodetect the density
91 of the available medium for multi-density devices.
93 possible to use either a 720 KB medium or a 1440 KB medium in a
94 high-density 3.5 inch standard floppy drive.
96 autodetection will only happen once at the first call to
98 for the device after inserting the medium.
99 This assumes the drive
100 offers proper changeline support so media changes can be detected by
102 To indicate a drive that does not have the changeline support,
103 this can be overridden using the per-drive device flags value of
105 (causing each call to
107 to perform the autodetection).
109 When trying to use a floppy device with special-density media, other
110 device nodes can be created, of the form
111 .Pa /dev/fd Ns Ar N . Ns Ar MMMM ,
114 is the drive number, and
116 is a number between one and four digits describing the device density.
117 Up to 15 additional subdevices per drive can be created that way.
119 administrator is free to decide on a policy how to assign these
121 The two common policies are to either implement subdevices
122 numbered 1 through 15, or to use a number that describes the medium
123 density in kilobytes.
124 Initially, each of those devices will be
125 configured to the maximal density that is possible for the drive type
126 (like 1200 KB for 5.25 inch HD drives or 1440 KB for 3.5 inch HD
128 The desired density to be used on that subdevice needs to be
132 Drive types are configured using the lower four bits of the per-drive
134 The following values can be specified:
135 .Bl -tag -width 2n -offset indent
137 5.25 inch double-density device with 40 cylinders (360 KB native
140 5.25 inch high-density device with 80 cylinders (1200 KB native
143 3.5 inch double-density device with 80 cylinders (720 KB native
146 3.5 inch high-density device with 80 cylinders (1440 KB native
149 3.5 inch extra-density device with 80 cylinders (2880 KB native
150 capacity, usage currently restricted to at most 1440 KB media)
152 Same as type 5, available for compatibility with some BIOSes
155 On IA32 architectures, the drive type can be specified as 0 for the
157 In that case, the CMOS configuration memory will be
158 consulted to obtain the value for that drive.
159 The ACPI probe automatically determines these values via the _FDE and
160 _FDI methods, but this can be overridden by specifying a drive type hint.
162 Normally, each configured drive will be probed at initialization
163 time, using a short seek sequence.
164 This is intended to find out about
165 drives that have been configured but are actually missing or
166 otherwise not responding.
167 (The ACPI probe method does not perform this seek.)
168 In some environments (like laptops with
169 detachable drives), it might be desirable to bypass this drive probe,
170 and pretend a drive to be there so the driver autoconfiguration will
171 work even if the drive is currently not present.
173 per-drive device flags value of
175 needs to be specified.
176 .Ss Programming Interface
177 In addition to the normal read and write functionality, the
179 driver offers a number of configurable options using
181 In order to access any of this functionality, programmers need to
182 include the header file
187 can be performed in two possible ways.
188 When opening the device
191 flag set, the device is opened in a normal way, which would cause the
192 main device nodes to perform automatic media density selection, and which
193 will yield a file descriptor that is fully available for any I/O operation
194 or any of the following
198 When opening the device with
200 set, automatic media density selection will be bypassed, and the device
201 remains in a half-opened state.
202 No actual I/O operations are possible, but
205 commands described below can be performed.
206 This mode is intended for
207 access to the device without the requirement to have an accessible
208 media present, like for status inquiries to the drive, or in order to
211 needs to be cleared before I/O operations are possible on the descriptor,
212 which requires a prior specification of the density using the
215 Operations that are not allowed on the half-opened
216 descriptor will cause an error value of
221 commands are currently available:
222 .Bl -tag -width ".Dv FD_READID"
224 Used to format a floppy disk medium.
225 Third argument is a pointer to a
226 .Vt "struct fd_formb"
227 specifying which track to format, and which parameters to fill into
228 the ID fields of the floppy disk medium.
230 Returns the current density definition record for the selected device.
231 Third argument is a pointer to
232 .Vt "struct fd_type" .
234 Adjusts the density definition of the selected device.
237 .Vt "struct fd_type" .
238 For the fixed-density subdevices (1 through 15 per drive), this
239 operation is restricted to a process with superuser privileges.
241 the auto-selecting subdevice 0, the operation is temporarily allowed
242 to any process, but this setting will be lost again upon the next
244 This can be used when formatting a new medium (which
245 will require to open the device using
247 and thus to later adjust the density using
250 Obtain the current drive options.
251 Third argument is a pointer to
253 containing a bitwise union of the following possible flag values:
254 .Bl -tag -width ".Dv FDOPT_NOERRLOG"
256 Do not automatically retry operations upon failure.
257 .It Dv FDOPT_NOERRLOG
260 kernel logs for failed I/O operations.
262 Do not indicate I/O errors when returning from
267 The caller is assumed to use
269 calls in order to inquire about the success of each operation.
271 is intended to allow even erroneous data from bad blocks to be
272 retrieved using normal I/O operations.
274 Device performs automatic density selection.
275 Unlike the above flags,
276 this one is read-only.
279 Set device options, see above for their meaning.
283 Drive options will always be cleared when closing the descriptor.
285 Clear the internal low-level error counter.
286 Normally, controller-level
287 I/O errors are only logged up to
289 errors (currently defined to 100).
290 This command resets the counter.
291 Requires superuser privileges.
293 Read one sector ID field from the floppy disk medium.
296 .Vt "struct fdc_readid" ,
297 where the read data will be returned.
298 Can be used to analyze a floppy
301 Return the recent floppy disk controller status, if available.
303 argument is a pointer to
304 .Vt "struct fdc_status" ,
305 where the status registers (ST0, ST1, ST2, C, H, R, and N) are being
308 will be caused if no recent status is available.
310 Returns the floppy disk drive type.
311 Third argument is a pointer to
312 .Vt "enum fd_drivetype" .
313 This type is the same as being used in the per-drive configuration
314 flags, or in the CMOS configuration data or ACPI namespace on IA32 systems.
316 .Sh DEPRECATION NOTICE
317 The PC Card attachment of this driver is scheduled for removal prior to the release of
320 .Bl -tag -width ".Pa /dev/fd*" -compact
322 floppy disk device nodes
335 This man page was initially written by
337 and later vastly rewritten by