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XX-5B6CF-19

May 2002

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Document:	wd
Order Number:	XX-5B6CF-19
Revision:
Pages:	2
Original Filename:	http://chdickman.com/qbus_ide/wd.pdf

OCR Text

WD(4)

NAME
wd − ATA/IDE disk controller interface

SYNOPSIS
/sys/conf/SYSTEM:
NWD wd_drives

# EIDE disk drive

/etc/dtab:
#Name Unit# Addr Vector Br Handler(s)
wd
?
171000 510
4 wdintr

# Comments
# EIDE disks

major device number(s):
raw: 27
block: 13
minor device encoding:
bits 0007 specify partition of WD drive
bits 0010 specify WD drive

DESCRIPTION
This is a driver for ATA-2 (IDE) compatible disk drives.
Files with minor device numbers 0 through 7 refer to various portions of drive 0; minor devices 8 through
15 refer to drive 1. Only two drives are supported under one IDE interface. The standard device names
begin with ‘‘wd’’ followed by the drive number and then a letter a-h for partitions 0-7 respectively. The
character ? stands here for a drive number in the range 0-7.
The block files access the disk via the system’s normal buffering mechanism and may be read and written
without regard to physical disk records. There is also a ‘raw’ interface which provides for direct transmission between the disk and the user’s read or write buffer. A single read or write call results in exactly one
I/O operation and therefore raw I/O is considerably more efficient when many words are transmitted. The
names of the raw files conventionally begin with an extra ‘r.’
In raw I/O the buffer must begin on a word (even) boundary, and counts should be a multiple of 512 bytes
(a disk sector). Likewise seek calls should specify a multiple of 512 bytes.

DISK SUPPORT
This driver configures the drive type of each drive when it is first opened. Partition information is read
from the disklabel. If there is no label or the label is corrupt then the ’a’ partition is used to span the entire
drive.
The wd?a partition is normally used for the root file system, the wd?b partition as a swap area, and the
wd?c partition for pack-pack copying (it maps the entire disk).

FILES
/dev/wd[0-7][a-h]
/dev/rwd[0-7][a-h]
/dev/MAKEDEV

script to create special files

SEE ALSO
hk(4), ram(4), ra(4), rk(4), rl(4), rp(4), rx(4), si(4), xp(4), dtab(5), autoconfig(8), disklabel(8)

DIAGNOSTICS
wd: insw: no DRQ count = %d Drive failed to set DRQ after count word transfers.
wd%d: %s LBA mode NOT supported! Drive IDENTIFY command indicated that drive does not support logical block addressing (LBA). Drive is NOT compatible with current driver.
wd: timeout waiting for BSY Drive set BSY too long.
wd: timeout waiting for DRDY Drive took too long to become ready.
wd: timeout waiting for DRQ Drive took too long to request data transfer.

January 16, 2002

WD(4)

wd: write error st = %o er = %o An error occured during a write operation. Status register and error register contents are reported.
wd: extra interrupt An interrupt occured when none was pending. The interrupt is cleared and the error is
ignored.
wd%d%c: hard read error bn %d An unrecoverable read error occured while reading the given block.
wd%d%c: hard write error bn %d An unrecoverable write error occured while reading the given block.

BUGS
In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, and write scribbles on the
tail of incomplete blocks. Thus, in programs that are likely to access raw devices, read, write and lseek(2)
should always deal in 512-byte multiples.
Only IDE drives capable of logical block addressing (LBA) are supported.
Data transfers only occur in PIO mode. This is a limitation of the interface and would be corrected if the
interface was capable of DMA.

January 16, 2002