A.4.5.1 Modifying SRBs

As mentioned in the preceding section, a SCSI miniport’s DriverEntry routine must request that the port driver allocate memory for SRB extensions if the miniport maintains per-request state information.

Otherwise, a SCSI miniport driver can write values into SRBs only for the following purposes and only in the following members:

• To return required status about each operation in the SrbStatus and ScsiStatus members

• If an underrun occurs, to update the DataTransferLength member

• If it supports auto request sense and transfers request-sense information, to update the SenseInfoBufferLength 

• If SRB_FLAGS_UNSPECIFIED_DIRECTION is set in the SrbFlags member and the HBA is a slave DMA device, to reset the SRB_FLAGS_DATA_IN or SRB_FLAGS_DATA_OUT, as appropriate to the current transfer request