RA(4)

NAME
ra - MSCP disk controller interface

SYNOPSIS
/sys/conf/SYSTEM:
	NRAC	ra_controllers	# NRAD controllers
	NRAD	ra_drives	# RX33/50, RC25, RD51/52/53/54, RA60/80/81/82
/etc/dtab:
	#Name	Unit#	Addr	Vector	Br	Handler(s)		# Comments
	ra	?	172150	154	5	raintr		# uda50, rqdx1/2/3
major device number(s):
	raw: 14
	block: 5
minor device encoding:
	bits 0007 specify partition of RA drive
	bits 0070 specify RA drive
	bits 0300 specify RA controller

DESCRIPTION
This is a driver for the DEC UDA-50 disk controller and for other compatible controllers. The UDA-50 communicates with the host through a packet oriented protocol termed the Mass Storage Control Protocol (MSCP). Consult the file <pdp/mscp.h> for a detailed description of this protocol.

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 ``ra'' 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 ra?a partition is normally used for the root file system, the ra?b partition as a swap area, and the ra?c partition for pack-pack copying (it maps the entire disk).

FILES
/dev/ra[0-7][a-h]
/dev/rra[0-7][a-h]
/dev/MAKEDEV    script to create special files

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

DIAGNOSTICS
rasa %o, state %d. (Additional status information given after a hard i/o error.) The values of the UDA-50 status register and the internal driver state are printed.

ra%d: interrupt in unknown state %d ignored. An interrupt was received when the driver was in an unknown internal state. Indicates a hardware problem or a driver bug.

ra%d: fatal error (%o). The UDA-50 indicated a ``fatal error'' in the status returned to the host. The contents of the status register are displayed.

ra%d,%d: OFFLINE. (Additional status information given after a hard i/o error.) A hard i/o error occurred because the drive was not on-line. The attached unit number and the MSCP unit numbers are printed.

status %o. (Additional status information given after a hard i/o error.) The status information returned from the UDA-50 is tacked onto the end of the hard error message printed on the console.

ra: unknown packet opcode=0%o. An MSCP packet of unknown type was received from the UDA-50. Check the cabling to the controller.

The following errors are interpretations of MSCP error messages returned by the UDA-50 to the host.

ra: %s error, controller error, event 0%o.

ra: %s error, host memory access error, event 0%o, addr 0%o.

ra: %s error, disk transfer error, unit %d, grp 0x%x, hdr 0x%x.

ra: %s error, SDI error, unit %d, event 0%o, hdr 0x%x.

ra: %s error, small disk error, unit %d, event 0%o, cyl %d.

ra: %s error, unknown error, unit %d, format 0%o, event 0%o.

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.