2.11BSD/man/cat4/dvhp.0
XP(4) UNIX Programmer's Manual XP(4)
NAME
xp - generic SMD moving-head disk
SYNOPSIS
/sys/conf/SYSTEM:
NXPC _x_p__c_o_n_t_r_o_l_l_e_r_s # Number of controllers
NXPD _x_p__d_r_i_v_e_s # RM02/03/05, RP04/05/06,
# CDC 9766, Fuji 160, etc.
BADSECT _N_O # Bad sector handling (see BUGS)
/etc/dtab:
#Name Unit# Addr Vector Br Handler(s) # Comments
xp ? 176700 254 5 xpintr # xp driver
major device number(s):
raw: 19
block: 10
minor device encoding:
bits 0007 specify partition of XP drive
bits 0370 specify XP drive
DESCRIPTION
The _x_p driver is a generic SMD storage module disk driver.
It can be adapted to most SMD controllers although
bootstrapping will not necessarily be directly possible.
The drives are numbered from 0 to _n on controller 0, from
_n+1 to _m on controller 1, etc. The drives may have dif-
ferent geometries.
The _x_p driver is unique amoungst 2BSD drivers in its number-
ing of drives. Other drivers (_r_a for example) number drives
0 thru 7 on controller 1, 8 thru 15 on controller 2 and so
on. _x_p on the other hand can have drives 0 and 1 on con-
troller 1, drives 2, 3, 4 and 5 on controller 2 and drives
6, 7 and 8 on controller 3. This is different from boot's
view of the world, so if you are booting from other than
unit 0 you may have to experiment a bit.
Files with minor device numbers 0 through 7 refer to various
portions of drive 0; minor devices 8 through 15 refer to
drive 1, etc. The standard device names begin with ``xp''
followed by the drive number and then a letter a-h for par-
titions 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 there-
fore raw I/O is considerably more efficient when many words
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XP(4) UNIX Programmer's Manual XP(4)
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 sec-
tor). Likewise _l_s_e_e_k calls should specify a multiple of 512
bytes.
DISK SUPPORT
Disks must be labeled using either the standalone _d_i_s_k_l_a_b_e_l
program on the boot tape or with the _d_i_s_k_l_a_b_e_l(8) program.
The kernel no longer attempts to determine the drive type
and geometry, instead reading this information from the
disklabel. There are no partition tables coded into the _x_p
driver, these must be placed on the drive with _d_i_s_k_l_a_b_e_l.
Special files should only be created for the partitions that
are actually used, as the overlap in these addresses could
lead to confusion otherwise. Traditionally the xp?a parti-
tion is normally used for the root file system, the xp?b
partition as a swap area, and the xp?c partition for pack-
pack copying (it maps the entire disk).
FILES
/dev/xp[0-7][a-h] block files
/dev/rxp[0-7][a-h] raw files
/dev/MAKEDEV script to create special files
/dev/MAKEDEV.local script to localize special files
SEE ALSO
hk(4), ra(4), ram(4), rk(4), rl(4), rp(4), rx(4), si(4),
dtab(5), autoconfig(8), newfs(8)
DIAGNOSTICS
xp%d%c: hard error sn%d cs2=%b er1=%b. An unrecoverable
error occurred during transfer of the specified sector of
the specified disk partition. The contents of the two error
registers are also printed in octal and symbolically with
bits decoded. The error was either unrecoverable, or a
large number of retry attempts (including offset positioning
and drive recalibration) could not recover the error.
xp%d: write locked. The write protect switch was set on the
drive when a write was attempted. The write operation is
not recoverable.
xp%d%c: soft ecc sn%d. A recoverable ECC error occurred on
the specified sector of the specified disk partition. This
happens normally a few times a week. If it happens more
frequently than this the sectors where the errors are occur-
ring should be checked to see if certain cylinders on the
pack, spots on the carriage of the drive or heads are
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XP(4) UNIX Programmer's Manual XP(4)
indicated.
xp%d: unknown device type 0%o. The number in the drive's
drive type register is unknown to the xp driver.
BUGS
In raw I/O _r_e_a_d and _w_r_i_t_e(2) truncate file offsets to 512-
byte block boundaries, and _w_r_i_t_e scribbles on the tail of
incomplete blocks. Thus, in programs that are likely to
access raw devices, _r_e_a_d, _w_r_i_t_e and _l_s_e_e_k(2) should always
deal in 512-byte multiples.
DEC-standard error logging should be supported.
The kernel uses partition 'h' to access the badblock infor-
mation. This should have been 'c' except that almost all of
the /etc/disktab entries (and thus existing systems) use 'h'
for this purpose. Unless you are very careful with _d_i_s_k_l_a_-
_b_e_l|(8) (to make certain that no data partition overlaps the
badblock area) you should probably leave BADSECT undefined
in the kernel config file.
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