.TITLE	VDDRV - VD: DRIVER
	.SBTTL	VDDRV - TITLE PAGE
	.IDENT	/V01.00/
;
; ************************************************************************
;                                                                        *
; THIS PROGRAM IS PROVIDED ON AN "AS IS" BASIS ONLY.  DIGITAL  EQUIPMENT *
; COMPUTER USER'S SOCIETY,  DIGITAL EQUIPMENT CORPORATION, MONSANTO, AND *
; THE AUTHOR DISCLAIM  ALL WARRANTIES ON THE PROGRAM,  INCLUDING WITHOUT *
; LIMITATION, ALL IMPLIED WARRANTIES OF MERCHANTABLITY AND FITNESS.      *
;									 *
; FULL PERMISSION AND CONSENT IS HEREBY GIVEN TO DECUS  AND TO THE DECUS *
; SPECIAL INTEREST  GROUPS  TO  REPRODUCE,  DISTRIBUTE,  AND PUBLISH AND *
; PERMIT  OTHERS  TO  REPRODUCE  IN  WHOLE  OR  IN PART, IN ANY FORM AND *
; WITHOUT RESTRICTION, THIS PROGRAM AND ANY INFORMATION RELATING THERETO *
;									 *
; ************************************************************************
;
; VD: (VIRTUAL DISK) DEVICE DRIVER.
;
; VERSION:	V01.00
;
; AUTHOR:	R.W. STAMERJOHN	MAPC	15-MAR-79
;
; MODIFICATION HISTORY:
;
;	NONE TO DATE

	.SBTTL	VDDRV - DECLARATIONS
;
; MACRO LIBRARY CALLS:
;
	.MCALL	PKTDF$			;DEFINE PACKET SYMBOLICS
	PKTDF$
	.MCALL	SCBDF$			;DEFINE SCB SYMBOLICS
	SCBDF$
	.MCALL	UCBDF$			;DEFINE UCB SYMBOLICS
	UCBDF$
;
; GLOBAL DECLARATIONS:
;
	.GLOBL	$VDTBL			;DRIVER DISPATCH TABLE
;
; GLOBAL REFERENCES:
;
	.GLOBL	$BLKCK			;BLOCK CHECK I/O FUNCTION
	.GLOBL	$DRQRQ			;QUEUE I/O REQUEST
	.GLOBL	$GTPKT			;GET I/O PACKET ROUTINE
	.GLOBL	$IOALT			;FINISH I/O PACKET
	.GLOBL	IE.IFC			;ILLEGAL FUNCTION CODE
	.GLOBL	IE.WLK			;DEVICE WRITE LOCKED
	.GLOBL	IO.RLB			;READ LOGICAL BLOCK

	.SBTTL	VDDRV - LOCAL DATA
;
; LOCAL DATA:
;
;	DEVICE DISPATCH TABLE
;
$VDTBL::				;REF. LABEL
	.WORD	VDINI			;DEVICE INITIATOR
	.WORD	VDCAN			;CANCEL I/O
	.WORD	VDTMO			;DEVICE TIMEOUT
	.WORD	VDPWF			;POWER RECOVERY

	.SBTTL	VDDRV * DRIVER CODE
;
; THIS DRIVER MEARLY RELOCATES THE LOGICAL BLOCK TO THE REAL LOGICAL
; BLOCK WITHIN THE DISK. THE MCR TASK AVD IS USED TO SETUP THE UCB
; FOR THIS OPERATION.
;
VDINI:	CALL	$GTPKT			;GET PACKET
	BCS	VDXIT			; IF CS - NO PACKET
;
; BLOCK CHECK FOR VIRTUAL DISK.
;
	CALL	$BLKCK			;BLOCK CHECK PARAMETERS
;
; PARAMETERS OK, CHECK IF ACCESS ALLOWED.
;
	MOV	U.NXT(R5),R0		;GET EXTENSION BLOCK ADDRESS
	CMPB	#IO.RLB/400,I.FCN+1(R3)	;CHECK FOR LEGAL FUNCTION
	BLO	2000$			; IF LO - BAD FUNCTION
	BEQ	1000$			;SKIP WRITE CHECK
	BIT	#XF.RON,X.FLG(R0)	;IS WRITE ACCESS ALLOWED?
	BNE	2010$			; IF NE - NO, ERROR
1000$:	ADD	X.OFF+2(R0),(R1)	;ADD IN LOW OFFSET
	ADC	-(R1)			; IN DOUBLE PRECISION
	ADD	X.OFF+0(R0),(R1)	;ADD IN HIGH OFFSET
;
; MARK THIS DRIVER NOT BUSY AND QUEUE PACKET TO NEXT DEVICE.
;
	BICB	#US.BSY,U.STS(R5)	;CLEAR UCB BUSY
	CLRB	S.STS(R4)		;CLEAR SCB BUSY
	MOV	R3,R1			;COPY PACKET ADDRESS
	MOV	X.UCB(R0),R5		;GET NEXT UCB
	CLR	I.LNK(R1)		;CLEAR LINK WORD
	MOV	R5,I.UCB(R1)		;SET NEW UCB
	CALLR	$DRQRQ			;QUEUE TO REAL DRIVER
;
; RETURN ERRORS TO USER.
;
2000$:	MOV	#IE.IFC&377,R0		;SET ERROR CODE
	BR	2020$			; CONTINUE
2010$:	MOV	#IE.WLK&377,R0		;SET ERROR CODE
2020$:	CALLR	$IOALT			;RETURN PACKET TO USER
;
; POWER FAIL SETS UCB OFFLINE. ALL OTHER DRIVER ENTRIES ARE NO-OP'S.
;
VDPWF:	BISB	#US.OFL,U.ST2(R5)	;MARK DRIVE OFFLINE
VDCAN:					;NO-OP
VDTMO:					;NO-OP
VDXIT:	RETURN				;RETURN TO CALLER

	.END