RA(4)		    UNIX Programmer's Manual		    RA(4)



NAME
     ra - MSCP disk controller interface

SYNOPSIS
     /sys/conf/SYSTEM:
	  NRAC _r_a__c_o_n_t_r_o_l_l_e_r_s # NRAD controllers
	  NRAD _r_a__d_r_i_v_e_s      # 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
     <_p_d_p/_m_s_c_p._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 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
     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 _s_e_e_k 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



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RA(4)		    UNIX Programmer's Manual		    RA(4)



     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 sys-
     tem, the ra?b partition as a swap area, and the ra?c parti-
     tion 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 mes-
     sages 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.



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RA(4)		    UNIX Programmer's Manual		    RA(4)



     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 _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.











































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