Windows Driver Kit: Storage Devices
SCSI_PASS_THROUGH
The SCSI_PASS_THROUGH structure is used in conjunction with an IOCTL_SCSI_PASS_THROUGH request to instruct the port driver to send an embedded SCSI command to the target device.
typedef struct _SCSI_PASS_THROUGH {
USHORT Length;
UCHAR ScsiStatus;
UCHAR PathId;
UCHAR TargetId;
UCHAR Lun;
UCHAR CdbLength;
UCHAR SenseInfoLength;
UCHAR DataIn;
ULONG DataTransferLength;
ULONG TimeOutValue;
ULONG_PTR DataBufferOffset;
ULONG SenseInfoOffset;
UCHAR Cdb[16];
}SCSI_PASS_THROUGH, *PSCSI_PASS_THROUGH;
Members
- Length
- Contains the value of sizeof(SCSI_PASS_THROUGH).
- ScsiStatus
- Reports the SCSI status that was returned by the HBA or the target device.
- PathId
- Indicates the SCSI port or bus for the request.
- TargetId
- Indicates the target controller or device on the bus.
- Lun
- Indicates the logical unit number of the device.
- CdbLength
- Indicates the size in bytes of the SCSI command descriptor block.
- SenseInfoLength
- Indicates the size in bytes of the request-sense buffer.
- DataIn
- Indicates whether the SCSI command will read or write data. This field must have one of three values:
| Data Transfer Type | Meaning |
|---|
| SCSI_IOCTL_DATA_IN | Read data from the device. |
| SCSI_IOCTL_DATA_OUT | Write data to the device. |
| SCSI_IOCTL_DATA_UNSPECIFIED | No data is transferred. |
- DataTransferLength
- Indicates the size in bytes of the data buffer. Many devices transfer chunks of data of pre-defined length. The value in DataTransferLength must be an integral multiple of this pre-defined, minimum length that is specified by the device. If an underrun occurs, the miniport driver 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.
- DataBufferOffset
- Contains an offset from the beginning of this structure to the data buffer. The offset must respect the data alignment requirements of the device.
- SenseInfoOffset
- Offset from the beginning of this structure to the request-sense buffer.
- Cdb
- Specifies the SCSI command descriptor block to be sent to the target device.
Comments
The SCSI_PASS_THROUGH structure is used with IOCTL_SCSI_PASS_THROUGH, which is a buffered device control request. To bypass buffering in system memory, callers should use IOCTL_SCSI_PASS_THROUGH_DIRECT. When handling an IOCTL_SCSI_PASS_THROUGH_DIRECT request, the system locks down the buffer in user memory and the device accesses this memory directly.
The members of SCSI_PASS_THROUGH correspond roughly to the members of a SCSI_REQUEST_BLOCK structure. The values of the DataIn member correspond to the SCSI_IOCTL_DATA_IN, SCSI_IOCTL_DATA_OUT, and SCSI_IOCTL_DATA_UNSPECIFIED flags assigned to SrbFlags member of SCSI_REQUEST_BLOCK.
Requirements
Headers: Declared in ntddscsi.h. Include ntddscsi.h.
See Also
IOCTL_SCSI_PASS_THROUGH, IOCTL_SCSI_PASS_THROUGH_DIRECT, SCSI_PASS_THROUGH_DIRECT, SCSI_REQUEST_BLOCK