HP-UX Reference (11i v1 00/12) - 5 Miscellaneous Topics, 7 Device (Special) Files, 9 General Information, Index (vol 9)

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STANDARD Printed by: Nora Chuang [nchuang] STANDARD

/build/1111/BRICK/man7/!!!intro.7

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disk(7) disk(7)

is a hardware-dependent value that can be queried with the DIOC_DESCRIBE ioctl call, which is

described below.

In addition to reading and writing data, the character-special ﬁle interface can used to obtain device speciﬁc

information and to perform special operations. These operations are controlled through use of ioctl calls.

Details related to these ioctls are contained in <sys/diskio.h >.

The DIOC_DESCRIBE ioctl can be used to obtain device speciﬁc identiﬁcation information. The informa-

tion returned includes the disk’s model identiﬁcation, the disk interface type, and the disk’s logical block

size.

The DIOC_CAPACITY ioctl can be used to obtain the capacity of a disk device in DEV_BSIZE units.

(DEV_BSIZE is deﬁned in <sys/param.h>).

The DIOC_EXCLUSIVE ioctl can be used to obtain and release exclusive access to a disk device.

Exclusive access is required for some special operations, such as media reformatting, and may be desirable

in other circumstances. The value one speciﬁes that exclusive access is requested. The value zero speciﬁes

the exclusive access should be released. Exclusive access causes other open requests to fail. Exclusive

access can only be granted when the device is not currently opened in block-mode and there is only one

open ﬁle table entry for that disk device (the one accessible to the exclusive access requester).

ERRORS

The following errors can be returned by a 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 dev-

ice can no longer be accessed.

[EINVAL] From an open() call: the device is not a disk device. For other calls: Invalid

request or parameter.

[EIO] I/O error (e.g., media defect or device communication problem).

WARNINGS

The interaction of block-special and character-special ﬁle access to the same

BLKDEV_IOSIZE

-sized block

is not speciﬁed, and in general is unpredictable.

On some systems, having both a mounted ﬁle system and a block special ﬁle open on the same device can

cause unpredictable results; this should be avoided if possible. This is because it may be possible for some

ﬁles to have private buffers in some systems.

Although disk devices have historically had small (typically 512-byte) block sizes, some disk devices (such as

optical disks and disk arrays) have relatively large block sizes. Applications using direct raw disk access

should use

ioctl() calls to determine appropriate I/O operation sizes and alignments.

Any disk with removable media (for example, ﬂoppy or CD-ROM) containing a mounted ﬁle system should

not be removed prior to being unmounted. Removal of disk media containing mounted ﬁle systems is likely

to result in ﬁle system errors and system panics.

DEPENDENCIES

disc3

Devices whose logical block size is less than DEV_BSIZE must be accessed on DEV_BSIZE boun-

daries and with transfer sizes that are multiples of

DEV_BSIZE. Disk ‘‘sections’’ 0 (zero) and 2 (two)

have exchanged meanings with HP-UX Release 10.0 and beyond. Whole disk is section 0.

AUTHOR

disk was developed by HP and AT&T.