floppy(7) floppy(7)
NAME [Toc] [Back]
floppy - direct flexible or ``floppy'' disk access
DESCRIPTION [Toc] [Back]
Flexible disk devices are removable-media disk devices that are
typically used to share data with other systems. Media types are
identified by physical size (such as 3.5-inch and 5.25-inch), number
of data surfaces (or sides), and data density. By convention,
flexible disk devices are named using the same conventions as those
used for other disk devices (see disk(7)).
Data can be stored on flexible disk media in a variety of logical
formats. The capacity of these devices is generally too small to hold
useful HP-UX file systems. Instead, DOS or LIF file systems (see
dosi
for a detailed description of these file systems)
are commonly used. Data can also be stored in an archive-utility
format. For example, tar and cpio are commonly used to share data
with other HP-UX systems (see tar(1) and cpio(1)).
Logical volumes are not supported on flexible disks. The floppy disk
does not support partitions. Section zero (0) is the only accessible
partition.
In addition to the various logical formats, data can be stored on
flexible disk media in a variety of physical data formats called
geometries. The following parameters are used to describe a flexible
disk geometry:
heads Number of surfaces (or sides) on the media that
contain valid data.
tracks Number of tracks on a single media surface or side
(the term cylinders is sometimes also used). This
value does not include spare tracks.
sectors Number of sectors in a single track. The number
of sectors that can fit on a track depends on the
bit density (as controlled by transfer rate and
media rotation rate) and the sector size.
sector size Number of bytes in a logical sector. Since all
I/O operations must be an integral number of
sectors in length, this parameter also indicates
the minimum character-special file I/O size.
transfer rate Media data rate in Kbits per second. The transfer
rate is an indirect means of representing bit
density. Bit density is measured in bits per
radian, and is the formal intra-track data density
parameter for standard specification. Transfer
rate is generally used to program flexible media
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devices and is therefore more appropriate for this
interface. Since the media rotation rate for most
flexible disk devices is standard, conversion
between these two representations is straightforward.
track density Number of tracks per inch. Some low density
formats can be supported on high-density drives by
skipping tracks during head stepping.
data encoding Encoding method used to store data. FM (frequency
modulation) and MFM (modified frequency
modulation) are the most common encoding methods;
RLL (run length limited) is a modification of MFM
that allows higher densities.
The following table shows some useful flexible disk media geometries
(without density information). The right-most column indicates which
mediainit -f option should be used to format media to the indicated
geometry (see mediainit(1)).
+--------------+----------+-----------+----+-----+------+------+----+
| Media Type | Use | Capacity | hd | trk | sect | size | -f |
+--------------+----------+-----------+----+-----+------+------+----+
| 3.5in DS DD | | 630,784 | 2 | 77 | 16 | 256 | 1 |
| 3.5in DS DD | | 655,360 | 2 | 80 | 16 | 256 | 21 |
| 3.5in DS DD | | 655,360 | 2 | 80 | 8 | 512 | 26 |
| 3.5in DS DD | | 709,632 | 2 | 77 | 9 | 512 | 2 |
| 3.5in DS DD | DOS 720K | 737,280 | 2 | 80 | 9 | 512 | 16 |
| 3.5in DS DD | | 788,480 | 2 | 77 | 5 | 1024 | 3 |
+--------------+----------+-----------+----+-----+------+------+----+
| 3.5in DS HD' | DOS 1.2M | 1,228,800 | 2 | 80 | 15 | 512 | 26 |
| 3.5in DS HD' | | 1,261,568 | 2 | 77 | 8 | 1024 | 22 |
+--------------+----------+-----------+----+-----+------+------+----+
| 3.5in DS HD | | 1,261,568 | 2 | 77 | 32 | 256 | 1 |
| 3.5in DS HD | | 1,419,264 | 2 | 77 | 18 | 512 | 2 |
| 3.5in DS HD | DOS 1.44M| 1,474,560 | 2 | 80 | 18 | 512 | 16 |
| 3.5in DS HD | | 1,567,960 | 2 | 77 | 10 | 1024 | 3 |
| 3.5in DS HD | | 1,638,400 | 2 | 80 | 10 | 1024 | 23 |
+--------------+----------+-----------+----+-----+------+------+----+
| 3.5in SD | DOS 120M | 120 MByte | 2 | 1736| 51-92| 512 | * |
+--------------+----------+-----------+----+-----+------+------+----+
| 5.25in DS | DOS 360K | 368,640 | 2 | 40 | 9 | 512 | 2 |
| 5.25in DS DD | | 655,360 | 2 | 80 | 8 | 512 | 26 |
| 5.25in DS HD | DOS 1.2M | 1,228,800 | 2 | 80 | 15 | 512 | 16 |
| 5.25in DS HD | | 1,261,568 | 2 | 77 | 8 | 1024 | 24 |
+--------------+----------+-----------+----+-----+------+------+----+
* For the LS-120 floppy, mediainit does not need the -f option. (The
option is ignored.) mediainit formats the disk as a 120-MByte floppy.
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The following table shows the density information for some standard
flexible disk media.
+--------------+----------+-----+------------+-----------+----------+
| Media Type | Bit Den | RPM | Trans Rate | Track Den | Encoding |
+--------------+----------+-----+------------+-----------+----------+
| 3.5in DS DD | 7,958 | 300 | 250 | 135 | MFM |
| 3.5in DS HD' | 13,262 | 360 | 500 | 135 | MFM |
| 3.5in DS HD | 15,916 | 300 | 500 | 135 | MFM |
+--------------+----------+-----+------------+-----------+----------+
| 3.5in SD | 33,660 | 720 | 500 | 2490 | RLL |
+--------------+----------+-----+------------+-----------+----------+
| 5.25in DS | 7,958 | 300 | 250 | 48 | MFM |
| 5.25in DS DD | 7,958 | 300 | 250 | 96 | MFM |
| 5.25in DS HD | 13,262 | 360 | 500 | 96 | MFM |
+--------------+----------+-----+------------+-----------+----------+
Abbreviations are interpreted as follows:
DS Double-sided media
DD Double-density media
HD High-density media
HD' High-density media (alternate media rotation rate)
SD LS-120 super disk
Normally each open() call causes the device and/or floppy device
driver to attempt to determine the geometry of the installed media.
As a result, the current flexible disk geometry is set to the
supported geometry that matches the physical data format on the media
currently installed in the device. To maintain reasonable open times,
not all possible media geometries are checked. Therefore, it is
possible that a flexible disk medium may contain valid data even
though its format is not recognized. This automatic geometry sensing
functionality may be disabled in some drivers by use of the O_NDELAY
flag in the open() call or device driver dependent minor numbers. The
Servers does not support this flag.
The FLOPPY_GET_INFO ioctl indicates the characteristics and current
status of a floppy device. Information for interpreting the media and
data_encoding fields can be found in <sys/floppy.h>. The following
macros are defined for decoding the status and valid fields. These
macros return a non-zero (true) value for the associated conditions.
FLOPPY_NO_MEDIA(x) /* Drive is empty */
FLOPPY_BLANK_MEDIA(x) /* Media geometry is not recognizable */
FLOPPY_WRITE_PROT(x) /* Media is write protected */
FLOPPY_MEDIA_CHANGED(x) /* Media has changed since last status
*/
FLOPPY_HIGH_DENSITY(x) /* Media has high density indication */
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The argument x in the above macros refers to the status or valid
fields of the FLOPPY_GET_INFO ioctl. Some floppy devices or floppy
device drivers may be unable to determine some status information.
The valid field indicates whether or not the corresponding status
information is meaningful. Applying a macro to the valid field
indicates whether or not the application of that same macro to the
status field results in a valid device status.
The FLOPPY_GET_GEOMETRY ioctl can be used to determine the flexible
disk device's current media geometry. Current geometry parameters are
indicated in the fields of the resultant floppy_geometry structure.
The FLOPPY_SET_GEOMETRY ioctl can be used to specify the desired media
geometry. Exclusive access to the device, obtained through use of the
DIOC_EXCLUSIVE ioctl (see disk(7)), is required prior to setting the
media geometry. Exclusive access is necessary to ensure that other
applications are not affected. The Servers does not support this
ioctl.
The FLOPPY_FORMAT_TRACK ioctl can be used to reformat a media track.
Exclusive access to the device, obtained through use of the
DIOC_EXCLUSIVE ioctl (see disk(7)), is required prior to reformatting
to ensure that other applications are not affected. The Servers does
not support this ioctl.
Flexible disk devices support the generic disk ioctls (see disk(7)),
typically used for hard disk devices. Flexible disk device drivers
may also support driver specific ioctls (see the appropriate driver
manual section).
The header file <sys/floppy.h> has useful information for flexiblemedia
device control. The following is included from <sys/floppy.h>:
/* ioctls for flexible (floppy) disk devices */
#define FLOPPY_GET_INFO _IOR('F', 1, struct floppy_info)
#define FLOPPY_GET_GEOMETRY _IOR('F', 2, struct floppy_geom)
#define FLOPPY_SET_GEOMETRY _IOW('F', 3, struct floppy_geom)
#define FLOPPY_FORMAT_TRACK _IOW('F', 4, struct floppy_format)
/* structure for FLOPPY_GET_INFO ioctl */
struct floppy_info {
unsigned media;
unsigned status;
unsigned valid;
};
/* structure for FLOPPY_GET_GEOMETRY and FLOPPY_SET_GEOMETRY ioctls */
struct floppy_geometry {
unsigned heads;
unsigned tracks;
unsigned sectors;
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unsigned sector_size;
unsigned transfer_rate;
unsigned track_density;
unsigned data_encoding;
};
/* structure for FLOPPY_FORMAT_TRACK ioctl */
struct floppy_format {
unsigned head;
unsigned track;
unsigned interleave;
};
ERRORS [Toc] [Back]
The following errors can be returned by a flexible-disk device-driver
call:
[EACCES] Required permission is denied for the the device
or operation.
[ENXIO] If resulting from an open call, this indicates
there is no device at the specified address. For
other calls, this indicates the specified address
is out of range or the device can no longer be
accessed.
[EINVAL] From an open() call: the device is not a floppy
device. For other calls: Invalid request or
parameter.
[EIO] I/O error (e.g., media defect or device
communication problem).
WARNINGS [Toc] [Back]
Media removal and/or replacement while the device is open is not
supported. A floppy disk containing a mounted file system should not
be removed prior to being unmounted. Removal of floppy disks
containing mounted file systems is likely to result in file system
errors, and system panics.
Reformatting flexible disk media from one geometry to another that
differs only in that it has fewer tracks can cause the automatic
geometry sensing functionality of open() to fail to recognize the new
media geometry. Bulk erasing (degaussing) the media or formatting the
media to a substantially different geometry prior to reformatting
prevents automatic geometry sensing problems.
Single track formatting may not be supported by some floppy devices.
Some devices permit configuration for geometries which they are unable
to support. The FLOPPY_SET_GEOMETRY ioctl for such a configuration
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may not result in an error. However, subsequent I/O operations will
fail.
DEPENDENCIES [Toc] [Back]
Workstations
Workstation device special files reside in the directories
/dev/rfloppy and /dev/floppy.
Servers [Toc] [Back]
A flexible disk can be opened with no media. However, capacity changes
resulting from subsequent media changes will not be recognized. (See
scsi_disk(7)).
Server device special files reside in the directories /dev/rdsk and
/dev/dsk.
The following table of Server Flexible Disk Media shows the disk
geometries supported. The media inserted in the drive is formatted
depending on the presence or absence of the HD hole in the flexible
disk cartridge. HD media is formatted as a 1.44M diskette and DD
media is formatted as a 720K diskette.
+--------------+----------+-----------+----+-----+------+------+
| Media Type | Use | Capacity | hd | trk | sect | size |
+--------------+----------+-----------+----+-----+------+------+
| 3.5in DS DD | DOS 720K | 737,280 | 2 | 80 | 9 | 512 |
+--------------+----------+-----------+----+-----+------+------+
| 3.5in DS HD | DOS 1.44M| 1,474,560 | 2 | 80 | 18 | 512 |
+--------------+----------+-----------+----+-----+------+------+
The following table shows the density information for the flexible
disk media supported:
+--------------+----------+-----+------------+-----------+----------+
| Media Type | Bit Den | RPM | Trans Rate | Track Den | Encoding |
+--------------+----------+-----+------------+-----------+----------+
| 3.5in DS DD | 7,958 | 300 | 250 | 135 | MFM |
| 3.5in DS HD | 15,916 | 300 | 500 | 135 | MFM |
+--------------+----------+-----+------------+-----------+----------+
The FLOPPY_GET_INFO and FLOPPY_GET_GEOMETRY ioctls are supported on
Servers.
SEE ALSO [Toc] [Back]
disk(7), mediainit(1), mknod(1M), dosif(4), lif(4), scsi(7),
scsi_disk(7).
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