SCSI_REQUEST

SCSI_REQUEST_BLOCK

typedef struct _SCSI_REQUEST_BLOCK { 
    USHORT Length; 
    UCHAR Function; 
    UCHAR SrbStatus; 
    UCHAR ScsiStatus; 
    UCHAR PathId; 
    UCHAR TargetId; 
    UCHAR Lun; 
    UCHAR QueueTag; 
    UCHAR QueueAction; 
    UCHAR CdbLength; 
    UCHAR SenseInfoBufferLength; 
    ULONG SrbFlags; 
    ULONG DataTransferLength; 
    ULONG TimeOutValue; 
    PVOID DataBuffer; 
    PVOID SenseInfoBuffer; 
    struct _SCSI_REQUEST_BLOCK *NextSrb; 
    PVOID OriginalRequest; 
    PVOID SrbExtension; 
    ULONG QueueSortKey; 
    UCHAR Cdb[16]; 
} SCSI_REQUEST_BLOCK, *PSCSI_REQUEST_BLOCK;

Members

Length

Specifies the size in bytes of this structure.

Function

Specifies the operation to be performed, which can be one of the following values:

Operation	Meaning
SRB_FUNCTION_EXECUTE_SCSI
	A SCSI device I/O request should be executed on the target logical unit.
SRB_FUNCTION_ABORT_COMMAND
	A SCSIMESS_ABORT message should be sent to cancel the request pointed to by the NextSrb member. If this is a tagged-queue request, a SCSIMESS_ABORT_WITH_TAG message should be used instead. If the indicated request has been completed, this request should be completed normally. Only the SRB Function, PathId, TargetId, Lun, and NextSrb members are valid.
SRB_FUNCTION_RESET_DEVICE
	The SCSI target controller should be reset using the SCSIMESS_BUS_DEVICE_RESET message. The miniport driver should complete any active requests for the target controller. Only the SRB Function, TargetId, and PathId members are valid.
SRB_FUNCTION_RESET_BUS
	The SCSI bus should be reset using the SCSIMESS_BUS_DEVICE_RESET message. A miniport driver receives this request only if a given request has timed out and a subsequent request to abort the timed-out request also has timed out. Only the SRB Function and PathId members are valid.
SRB_FUNCTION_TERMINATE_IO
	A SCSIMESS_TERMINATE_IO_PROCESS message should be sent to cancel the request pointed to by the NextSrb member. If the indicated request has already completed, this request should be completed normally. Only the SRB Function, PathId, TargetId, Lun, and NextSrb members are valid.
SRB_FUNCTION_RELEASE_RECOVERY
	A SCSIMESS_RELEASE_RECOVERY message should be sent to the target controller. Only the SRB Function, PathId, TargetId, and Lun members are valid.
SRB_FUNCTION_RECEIVE_EVENT
	The HBA should be prepared to receive an asynchronous event notification from the addressed target. The SRB DataBuffer member indicates where the data should be placed.
SRB_FUNCTION_SHUTDOWN
	The system is being shut down. This request is sent to a miniport driver only if it set CachesData to TRUE in the PORT_CONFIGURATION_INFORMATION for the HBA. Such a miniport driver can receive several of these notifications before all system activity actually stops. However, the last shutdown notification will occur after the last start I/O. Only the SRB Function, PathId, TargetId, and Lun members are valid.
SRB_FUNCTION_FLUSH
	The miniport should flush any cached data for the target device. This request is sent to the miniport driver only if it set CachesData to TRUE in the PORT_CONFIGURATION_INFORMATION for the HBA. Only the SRB Function, PathId, TargetId, and Lun members are valid.
SRB_FUNCTION_IO_CONTROL
	The request is an I/O control request, originating in a user-mode application with a dedicated HBA. The SRB DataBuffer points to an SRB_IO_CONTROL header followed by the data area. The value in DataBuffer can be used by the driver, regardless of the value of MapBuffers. Only the SRB Function, SrbFlags, TimeOutValue, DataBuffer, and DataTransferLength members are valid, along with the SrbExtension member if the miniport driver requested SRB extensions when it initialized. If a miniport driver controls an application-dedicated HBA so it supports this request, the miniport should execute the request and notify the OS-specific port driver when the SRB has completed, using the normal mechanism of calls to ScsiPortNotification with RequestComplete and NextRequest.

SrbStatus

Returns the status of the completed request. This member should be set by the miniport driver before it notifies the OS-specific driver that the request has completed by calling ScsiPortNotification with RequestComplete. The value of this member can be one of the following:

Status	Meaning
SRB_STATUS_PENDING
	Indicates the request is in progress. The OS-specific port driver initializes SrbStatus to this value. A miniport driver should never set the SrbStatus member to this value.
SRB_STATUS_SUCCESS
	Indicates the request was completed successfully.
SRB_STATUS_ABORTED
	Indicates the request was aborted as directed by the port driver. A miniport driver sets this status in the NextSrb for a successful SRB_FUNCTION_ABORT_COMMAND request.
SRB_STATUS_ABORT_FAILED
	Indicates an attempt to abort the request failed. Return this status for an SRB_FUNCTION_ABORT_COMMAND request when the specified request cannot be located.
SRB_STATUS_ERROR
	Indicates the request was completed with an error in the SCSI bus status.
SRB_STATUS_BUSY
	Indicates the miniport or target device could not accept the request at this time. The OS-specific port driver will resubmit the request later.
SRB_STATUS_INVALID_REQUEST
	Indicates the miniport driver does not support the given request.
SRB_STATUS_NO_DEVICE
	Indicates the device did not respond.
SRB_STATUS_TIMEOUT
	Indicates the request timed out.
SRB_STATUS_SELECTION_TIMEOUT
	Indicates the SCSI device selection timed out.
SRB_STATUS_COMMAND_TIMEOUT
	Indicates the target did not complete the command within the time limit.
SRB_STATUS_MESSAGE_REJECTED
	Indicates the target rejected a message. This is normally returned only for such message-type requests as SRB_FUNCTION_TERMINATE_IO.
SRB_STATUS_BUS_RESET
	Indicates a bus reset occurred while this request was being executed.
SRB_STATUS_PARITY_ERROR
	Indicates a parity error occurred on the SCSI bus and that a retry failed.
SRB_STATUS_REQUEST_SENSE_FAILED
	Indicates the request-sense command failed. This is returned only if the HBA performs auto request sense and the miniport driver set AutoRequestSense to TRUE in the PORT_CONFIGURATION_INFORMATION for this HBA.
SRB_STATUS_NO_HBA
	Indicates the HBA does not respond.
SRB_STATUS_DATA_OVERRUN
	Indicates that a data overrun or underrun error occurred. The miniport also must update the SRB’s DataTransferLength member to indicate how much data actually was transferred if an underrun occurs.
SRB_STATUS_UNEXPECTED_BUS_FREE
	Indicates the target disconnected unexpectedly.
SRB_STATUS_PHASE_SEQUENCE_FAILURE
	Indicates the HBA detected an illegal phase sequence failure error.
SRB_STATUS_REQUEST_FLUSHED
	Indicates the request for status was stopped.
SRB_STATUS_BAD_FUNCTION
	Indicates the SRB Function code is not supported.
SRB_STATUS_INVALID_PATH_ID
	Indicates the PathId specified in the SRB does not exist.
SRB_STATUS_INVALID_TARGET_ID
	Indicates the TargetID value in the SRB is invalid.
SRB_STATUS_INVALID_LUN
	Indicates the Lun value in the SRB is invalid.
SRB_STATUS_ERROR_RECOVERY
	Indicates the request was completed with an error in the SCSI bus status and that the SCSI INITIATE RECOVERY message was received.
SRB_STATUS_AUTOSENSE_VALID
	Indicates information returned in the SenseInfoBuffer is valid.
SRB_STATUS_QUEUE_FROZEN
	A miniport driver should never set the SrbStatus member to this value. The Windows NT port driver can set this value to inform a SCSI class driver that its queue of requests for a particular peripheral has been frozen.

ScsiStatus

Returns the SCSI status that was returned by the HBA or target device. If the status is not SUCCESS, the miniport driver should set the SrbStatus member to SRB_STATUS_ERROR.

PathId

Indicates the SCSI port or bus for the request. This value is zero-based.

TargetId

Indicates the target controller or device on the bus.

Lun

Indicates the logical unit number of the device.

QueueTag

Is the queue-tag value assigned by the OS-specific port driver. If this member is used for tagged queueing, the HBA supports internal queueing of requests to LUs and the miniport driver set TaggedQueuing to TRUE in the PORT_CONFIGURATION_INFORMATION for this HBA.

QueueAction

Indicates the tagged-queueing message to be used when the SRB_FLAGS_QUEUE_ACTION_ENABLE flag is set. The value can be one of the following: SRB_SIMPLE_TAG_REQUEST, SRB_HEAD_OF_QUEUE_TAG_REQUEST, or SRB_ORDERED_QUEUE_TAG_REQUEST, as defined according to the SCSI-II specification.

CdbLength

Indicates the size in bytes of the SCSI command descriptor block.

SenseInfoBufferLength

Indicates the size in bytes of the request-sense buffer.

SrbFlags

Indicates various parameters and options about the request. SrbFlags is read-only, except when SRB_FLAGS_UNSPECIFIED_DIRECTION is set and miniport drivers of slave DMA adapters are required to update SRB_FLAGS_DATA_IN or SRB_FLAGS_DATA_OUT. This member can have one or more of the following flags set:

Value	Meaning
SRB_FLAGS_QUEUE_ACTION_ENABLE
	Indicates tagged-queue actions are to be enabled.
SRB_FLAGS_DISABLE_AUTOSENSE
	Indicates that request-sense information should not be returned.
SRB_FLAGS_DATA_IN
	Indicates data will be transferred from the device to the system.
SRB_FLAGS_DATA_OUT
	Indicates data will be transferred from the system to the device.
SRB_FLAGS_UNSPECIFIED_DIRECTION
	Defined for backward compatibility with the ASPI/CAM SCSI interfaces, this flag indicates that the transfer direction could be either of the preceding because both of the preceding flags are set. If this flag is set, a miniport driver should determine the transfer direction by examining the data phase for the target on the SCSI bus. If its HBA is a slave DMA device, such a miniport must update SRB_FLAGS_DATA_OUT or SRB_FLAGS_DATA_IN to the correct value before it calls ScsiPortIoMapTransfer.
SRB_FLAGS_NO_DATA_TRANSFER
	Indicates no data transfer with this request. If this is set, the flags SRB_FLAGS_DATA_OUT, SRB_FLAGS_DATA_IN, and SRB_FLAGS_UNSPECIFIED_DIRECTION are clear.
SRB_FLAGS_DISABLE_SYNCH_TRANSFER
	Indicates the HBA, if possible, should not perform a synchronous negotiation for this transfer request.
SRB_FLAGS_DISABLE_DISCONNECT
	Indicates the HBA should not allow the target to disconnect from the SCSI bus during processing of this request.
SRB_FLAGS_BYPASS_FROZEN_QUEUE
	Is irrelevant to miniport drivers.
SRB_FLAGS_NO_QUEUE_FREEZE
	Is irrelevant to miniport drivers.
SRB_FLAGS_IS_ACTIVE
	Is irrelevant to miniport drivers.
SRB_FLAGS_ALLOCATED_FROM_ZONE
	Is irrelevant to miniport drivers. To a Windows NT class driver, this indicates whether the SRB was allocated from a zone buffer. If this flag is set, the class driver must call ExInterlockedFreeToZone to release the SRB; otherwise, it must call ExFreePool.
SRB_FLAGS_SGLIST_FROM_POOL
	Is irrelevant to miniport drivers. To a Windows NT class driver, this indicates that memory for a scatter/gather list was allocated from nonpaged pool. If this flag is set, the class driver must call ExFreePool to release the memory after the SRB is completed.

DataTransferLength

Indicates the size in bytes of the data buffer. If an underrun occurs, the miniport must update this member to the number of bytes actually transferred.

TimeOutValue

Indicates the interval in seconds that the request can execute before the OS-specific port driver might consider it timed out. Miniport drivers are not required to time requests because the port driver already does.

DataBuffer

Points to the data buffer. Miniport drivers should not use this value as a data pointer unless the miniport set MapBuffers to TRUE in the PORT_CONFIGURATION_INFORMATION for the HBA. In the case of SRB_FUNCTION_IO_CONTROL requests, however, miniport drivers can use this value as a data pointer regardless of the value of MapBuffers.

SenseInfoBuffer

Points to the request-sense buffer. A miniport driver is not required to provide request-sense data after a CHECK CONDITION. If it does, such a driver should not use the SenseInfoBuffer value as a data pointer unless the miniport set MapBuffers to TRUE in the PORT_CONFIGURATION_INFORMATION for the HBA. The physical address of the buffer can be obtained by calling ScsiPortGetPhysicalAddress.

NextSrb

Indicates the SCSI_REQUEST_BLOCK to which this request applies. Only a small subset of requests use a second SRB, for example SRB_FUNCTION_ABORT_COMMAND.

OriginalRequest

Points to the IRP for this request.

SrbExtension

Points to the Srb extension. A miniport must not use this member if it set SrbExtensionSize to zero in the SCSI_HW_INITIALIZATION_DATA. The memory at SrbExtension is not initialized by the OS-specific port driver, and the miniport-determined data can be accessed directly by the HBA. The corresponding physical address can be obtained by calling ScsiPortGetPhysicalAddress with the SrbExtension pointer.

QueueSortKey

Specifies the offset from the start of the media or zero, depending on the type of the target device.

Cdb

Specifies the SCSI-II command descriptor block to be sent to the target device.

Comments

Windows NT SCSI class and filter drivers can send SRBs with the following Function values to the system port driver:

SRB_FUNCTION_CLAIM_DEVICE to indicate that the class driver supports a peripheral identified in the SRB by the PathId, TargetId, and Lun members.
SRB_ATTACH_DEVICE to indicate that a filter driver, layered above a class driver, wants requests for a particular peripheral to be routed first to the filter driver.
SRB_FUNCTION_RELEASE_DEVICE to indicate that a class driver is releasing its claim on a particular peripheral.
SRB_FUNCTION_FLUSH_QUEUE to request cancellation of any requests currently queued in the port driver to a particular peripheral.
SRB_FUNCTION_RELEASE_QUEUE to request that the port driver release a frozen queue of requests to a particular peripheral.

The preceding SRB_FUNCTION_XXX are never set in SRBs sent to SCSI miniport drivers. SRB_FUNCTION_REMOVE_DEVICE is defined for use in future versions of the system. It, too, is never set in SRBs sent to SCSI miniport drivers.

SCSI_REQUEST_BLOCK

Members

Comments

See Also