RA(4)							     Kernel Interfaces Manual							     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 copy-
       ing (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 inter-
       nal 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.

3rd Berkeley Distribution					 September 6, 1987							     RA(4)