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Inside Macintosh: Devices /

Chapter 4 - SCSI Manager 4.3 / SCSI Manager 4.3 Reference

SCSI Manager 4.3 Functions / Client Functions

SCSIReleaseQ

You use the SCSIReleaseQ function to release a frozen queue for a LUN.

OSErr SCSIAction(SCSI_PB *scsiPB);

scsiPB

A pointer to a SCSI Manager parameter block.

-->	scsiPBLength	UInt16	The size of the parameter block.
-->	scsiFunctionCode	UInt8	The SCSIReleaseQ function selector code (0x04).
<--	scsiResult	OSErr	The returned result code.
-->	scsiDevice	DeviceIdent	The device identification record.
-->	scsiCompletion	CallbackProc	Unused. Must be set to nil.

DESCRIPTION

The SCSIReleaseQ function releases a frozen I/O queue for the logical unit number specified in the scsiDevice field. If an I/O request returns with the scsiSIMQFrozen flag set in the scsiResultFlags field, you must call this function to restore normal operation.

Queue freezing provides the opportunity to insert error-handling requests at the beginning of the queue using the scsiSIMQHead flag. You then release the queue using this function. Subsequent errors will continue to freeze the queue, allowing you to step through the queue one request at a time without aborting any other pending requests.

Because this function is always executed synchronously, the scsiCompletion field must be set to nil. Unlike other synchronous functions, however, you can call SCSIReleaseQ from a completion routine.

RESULT CODES

noErr	0	No error
scsiIDInvalid	-7866	The initiator ID is invalid
scsiLUNInvalid	-7867	The logical unit number is invalid
scsiTIDInvalid	-7868	The target ID is invalid
scsiBusInvalid	-7869	The bus ID is invalid
scsiRequestInvalid	-7870	The parameter block request is invalid
scsiPBLengthError	-7872	The parameter block is too small for this SIM
scsiQLinkInvalid	-7881	The qLink field was not 0

SEE ALSO

See "Error Recovery Techniques" on page 4-10 for more information about queue freezing.