FD

NAME

SYNOPSIS

DESCRIPTION

/dev/fd<unit>a

/dev/rfd<unit><partition>

where <partition> is either ``a'' or ``b.'' Partition b of the character device, such as fd0b, is a special device called the live partition. I/O to/from the live partition is used to access disks that do not have a valid label, and to access portions of disks normally inaccessible to the read() and write() calls --- for example, the front porch. (Reading and writing the ``a'' partition of the character or block device requires a valid label on the disk.) I/O using the live partition has the following restrictions:

*

Reads and writes must start on a sector boundary.

*

The length of reads and writes must be an integral multiple of the sector size.

Multiple Disk Format Support

The fd driver is capable of dealing with disks of 3 capacities: 720 KByte, 1.4 MByte, and 2.8 MByte (all sizes formatted). The driver determines the capacity of a disk when it is inserted (or at boot time) by attempting to read headers and data at all densities until headers and data are read successfully. The sector size of the disk is also determined in this manner; legal sector sizes are 512 and 1024 bytes per sector. The capacity of a disk, along with other format parameters, can be determined at the user level by executing a FDIOCGFORM ioctl (see below).  

Multiple Volume Support (M68K only)

The fd driver supports drives with removable media; therefore, in a manner similar to the sd(4) and od(4) drivers, the devices in /dev/*fd* refer to volumes, not to drives. One physical drive can have multiple volumes associated with it any any given time. Each drive has associated with it at most one volume at boot time --- drive 0 is associated with volume 0 (/dev/rfd0? and /dev/fd0a) if a disk is present at boot time, drive 1 with volume 1, etc. Henceforth, volumes can be assigned to a drive if one of the following occurs:

*

A DKIOCEJECT ioctl is executed on a volume, but the device remains open. Then a new volume (removable disk) is inserted in the empty drive. This new disk will be assigned to the next available volume number, and will henceforth be associated with this drive.

*

An open() call is executed on a volume not currently assigned to a drive. (See the DKIOCFREEVOL ioctl, below.)

In both of these cases, the following occurs when an I/O is attempted on a volume not currently present in a drive:

1.

The volume currently present in the desired drive is ejected. (If any references still remain to this device, the volume will be ``remembered,'' and will not be reassigned; otherwise the volume information is discarded, and the volume may be reassigned at a later time.)

2.

An alert panel is displayed, asking for the desired volume (by name, if known).

3.

The user takes one of two actions:

*

The desired volume is inserted; the alert panel is then removed.

*

The user clicks on the ``Cancel'' button in the alert panel. This causes the I/O to the missing volume to be aborted with a status of ENODEV.

Another feature of removable media support is automatic mounting of newly inserted volumes. If a disk is inserted in an empty drive, the disk will be mounted if it has a valid label and is in a consistent (``clean'') state. If it does not have a valid label, or has a file system in an inconsistent state, the user will be asked by the Workspace Manager (via an alert panel) if he/she wants to initialize it (or repair it, if ``unclean''). Answering in the affirmative ultimately results in the disk being mounted in the root directory.

The following operations are allowed by the Floppy disk driver:

open()

See open(2).

close()

See close(2).

read()

See read(2).

write()

See write(2).

strategy()

This is the standard block device entry point used by the UNIX file system, and is only valid for a block disk device.

ioctl()

The general form of an ioctl() call is

ioctl(int d, u_int request, char *argp)

The following ioctl requests are currently defined (see /NextDeveloper/Headers/bsd/dev/disk.h and /NextDeveloper/Headers/bsd/dev/fd_extern.h):

DKIOCGLABEL

Get disk label; argp points to a pointer to a struct disk_label (see /NextDeveloper/Headers/bsd/dev/disk.h). Copies the label of the current disk into user address space.

DKIOCSLABEL

Write disk label; argp points to a pointer to a struct disk_label. (Must be superuser to execute this call.)

DKIOCINFO

Get drive info; argp points to a struct drive_info (see /NextDeveloper/Headers/bsd/dev/disk.h).

FDIOCGFORM

Get disk format parameters; argp points to a struct fd_format_info (see /NextDeveloper/Headers/bsd/dev/fd_extern.h).

DKIOCEJECT

Eject the disk. Only valid for drives with removable media. See ``Multiple Volume Support.''

FDIOCSDENS

Set disk density; argp points to an int, with legal values of *argp being as follows:

value	unformatted capacity	formatted capacity
FD_DENS_NONE	unformatted	0
FD_DENS_1	1 MByte	720 KBytes
FD_DENS_2	2 MByte	1.4 MBytes
FD_DENS_4	4 MByte	2.8 MBytes

These constants are defined in /NextDeveloper/Headers/bsd/dev/fd_extern.h.

FDIOCSSIZE

Set Sector size (in bytes); argp points to an int, with legal values being 512 and 1024.

FDIOCSGAPL

Set Gap3 length (in bytes); argp points to an int. Gap3 is the length of the write splice at the end of a sector.

FDIOCSIRETRY

Set inner_retry_count; argp points to an int. Upon detection of a media error, the fd driver will attempt inner_retry_count retries; if these fail, a recalibrate is performed and another inner_retry_count retries attempted. This loop (inner_retry_count attempts followed by a recalibrate) will be repeated up to outer_retry_count times. If none of the retries succeed, the I/O is aborted.

FDIOCGIRETRY

Get inner_retry_count; argp points to an int.

FDIOCSOETRY

Get outer_retry_count; argp points to an int.

FDIOCGORETRY

Get outer_retry_count; argp points to an int.

DKIOCGFREEVOL

Get the number of the next free volume; argp points to an int. This ioctl is normally executed on the Floppy Disk Controller device, /dev/fdc0. It is used when an application wants to determine the volume number not currently in use. if this ioctl returns a value of 3, for example, a subsequent open of /dev/rfd3a will result in an alert panel requesting a new disk for volume 3.

FDIOCREQ

Execute an arbitrary command on the Intel 82077 Floppy Disk Controller using the fd_ioreq mechanism. (You must be superuser to execute this call.)

For FDIOCREQ, argp points to a struct fd_ioreq, which is defined in /NextDeveloper/Headers/bsd/dev/fd_extern.h, as are all other constants used with this mechanism. This struct contains both the input to the fd driver required for execution of a command as well as the status block upon return. The following status is provided:

fd_ioreq.status

Indicates success, I/O timeout, Media Error, DMA overrun, etc.

fd_ioreq.cmd_bytes_xfr

Number of command bytes actually transferred to the 82077.

fd_ioreq.bytes_xfr

Number of data bytes actually transferred via the 82077.

fd_ioreq.stat_bytes_xfr

Number of status bytes actually transferred from the 82077.

fd_ioreq.drive_stat

This is a struct fd_drive_stat. It contains Media ID, Write protect status, the state of the motor, and a bit indicating the presence of the drive.

FILES

/NextDeveloper/Headers/bsd/dev/fd_extern.h
/NextDeveloper/Headers/bsd/dev/disk.h
/dev/rfd??
/dev/fd?a
/dev/fdc0

SEE ALSO

Index

NAME

SYNOPSIS

DESCRIPTION

Multiple Disk Format Support

Multiple Volume Support (M68K only)

FILES

SEE ALSO