From:	SMTP%"critz@star.enet.dec.com" 20-SEP-1993 08:40:29.07
To:	EVERHART
CC:	
Subj:	Re: How to find UCB address from device name?

X-Newsgroups: comp.os.vms
From: critz@star.enet.dec.com (Richard Critz)
Subject: Re: How to find UCB address from device name?
Message-Id: <1993Sep16.165001.29067@nntpd.lkg.dec.com>
Lines: 71
Sender: usenet@nntpd.lkg.dec.com (USENET News System)
Reply-To: critz@star.enet.dec.com (Richard Critz)
Organization: Digital Equipment Corporation, Nashua, NH
Date: Thu, 16 Sep 1993 16:50:01 GMT
To: Info-VAX@kl.sri.com
X-Gateway-Source-Info: USENET


While the preferred mechanism for getting the UCB address given the device
name is to:

	1) $ASSIGN a channel to the device
	2) call IOC$VERIFYCHAN to locate the CCB for the channel
		(DO *NOT* try to do it yourself.  You'll fail on
		 OpenVMS AXP V1.5 and later since I changed the
		 algorithm for mapping channel number to CCB.  Just
		 use the routine)
	3) Fetch the UCB from the appropriate field in the CCB
		(CCB$L_UCB)

You can also use IOC$SEARCHDEV (this routine is pageable but has a simpler
interface) or IOC$SEARCHINT.

IOC$SEARCHDEV is called as follows:

;+
;
; IOC$SEARCH - general I/O database search
; IOC$SEARCHDEV - search for specific physical device
; IOC$SEARCHALL - generic search for any device
;
; This routine searches the I/O database for the specified device, using
; the specified search rules. Depending on the search, a lock may or may
; not be taken out on the device when it is found.
;
; INPUTS:
;
;       R1 = address of descriptor of device / logical name string
;       R2 = flags
;       R3 = address to store lock value block
;       I/O database mutex held, IPL 2
;
; OUTPUTS:
;
;       R0 = SS$_NORMAL - device found
;          = SS$_ACCVIO - name string is not readable
;          = SS$_NONLOCAL - nonlocal device
;          = SS$_IVLOGNAM - invalid logical name (e.g., too long)
;          = SS$_TOOMANYLNAM - max. logical name recursion exceeded
;          = SS$_IVDEVNAM - invalid device name string
;          = SS$_NOSUCHDEV - device not found
;          = SS$_NODEVAVL - device exists but not available according to rules
;          = SS$_DEVALLOC - device allocated to other user
;          = SS$_NOPRIV - failed device protection
;          = SS$_TEMPLATEDEV - can't allocate template device
;          = SS$_DEVMOUNT - device already mounted
;          = SS$_DEVOFFLINE - device marked offline
;       R1 = UCB
;       R2 = DDB
;       R3 = system block
;       R4 - R11 preserved
;
;       Note: If failure, R1 - R3 point to the last structures looked at.
;
;       R2 and R3 are input only to IOC$SEARCH.
;
;       IOC$SEARCHDEV:  R2 = IOC$M_PHY ! IOC$M_ANY
;                       R3 = 0
;       IOC$SEARCHALL:  R2 = IOC$M_ANY ! IOC$M_LOCAL
;                       R3 = 0
;
;-

--
-----------------------------------------------------------------------------
Richard Critz					      critz@star.enet.dec.com
      -- I speak only for myself; I make no commitments for Digital. --
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