Processing Tape Device Control Requests

All tape miniclass drivers must report status using the values listed in the TAPE_STATUS enumerator. However, when the tape class driver completes an I/O control request, it reports status using the equivalent NT Status Values. The following table provides a mapping between TAPE_STATUS values and their equivalent NT status values:

NT Status Value	Tape Status Value
STATUS_INSUFFICIENT_RESOURCES	TAPE_STATUS_INSUFFICIENT_RESOURCES
STATUS_NOT_IMPLEMENTED	TAPE_STATUS_NOT_IMPLEMENTED
STATUS_INVALID_DEVICE_REQUEST	TAPE_STATUS_INVALID_DEVICE_REQUEST
STATUS_INVALID_PARAMETER	TAPE_STATUS_INVALID_PARAMETER
STATUS_VERIFY_REQUIRED	TAPE_STATUS_MEDIA_CHANGED
STATUS_BUS_RESET	TAPE_STATUS_BUS_RESET
STATUS_SETMARK_DETECTED	TAPE_STATUS_SETMARK_DETECTED
STATUS_FILEMARK_DETECTED	TAPE_STATUS_FILEMARK_DETECTED
STATUS_BEGINNING_OF_MEDIA	TAPE_STATUS_BEGINNING_OF_MEDIA
STATUS_END_OF_MEDIA	TAPE_STATUS_END_OF_MEDIA
STATUS_BUFFER_OVERFLOW	TAPE_STATUS_BUFFER_OVERFLOW
STATUS_NO_DATA_DETECTED	TAPE_STATUS_NO_DATA_DETECTED
STATUS_EOM_OVERFLOW	TAPE_STATUS_EOM_OVERFLOW
STATUS_NO_MEDIA	TAPE_STATUS_NO_MEDIA
STATUS_IO_DEVICE_ERROR	TAPE_STATUS_IO_DEVICE_ERROR
STATUS_UNRECOGNIZED_MEDIA	TAPE_STATUS_UNRECOGNIZED_MEDIA
STATUS_DEVICE_NOT_READY	TAPE_STATUS_DEVICE_NOT_READY
STATUS_MEDIA_WRITE_PROTECTED	TAPE_STATUS_MEDIA_WRITE_PROTECTED
STATUS_DEVICE_DATA_ERROR	TAPE_STATUS_DEVICE_DATA_ERROR
STATUS_NO_SUCH_DEVICE	TAPE_STATUS_NO_SUCH_DEVICE
STATUS_INVALID_BLOCK_LENGTH	TAPE_STATUS_INVALID_BLOCK_LENGTH
STATUS_IO_TIMEOUT	TAPE_STATUS_IO_TIMEOUT
STATUS_DEVICE_NOT_CONNECTED	TAPE_STATUS_DEVICE_NOT_CONNECTED
STATUS_DATA_OVERRUN	TAPE_STATUS_DATA_OVERRUN
STATUS_DEVICE_BUSY	TAPE_STATUS_DEVICE_BUSY
STATUS_DEVICE_REQUIRES_CLEANING	TAPE_STATUS_REQUIRES_CLEANING
STATUS_CLEANER_CARTRIDGE_INSTALLED	TAPE_STATUS_CLEANER_CARTRIDGE_INSTALLED

Whenever the class driver must call a miniclass routine more than once to complete a request, the miniclass driver uses the return status to indicate whether the request is complete or whether the routine should be called again. The tape class driver maintains a zero-based count of the number of times that it has called the miniclass routine for a given request and passes that count to the routine as the CallNumber parameter.

A miniclass routine returns one of the following status values to indicate that the class driver should call the routine again:

• TAPE_STATUS_SEND_SRB_AND_CALLBACK

  This return value directs the tape class driver to send the SRB to the device. A tape miniclass routine usually returns this status after filling in the SRB passed by the tape class driver. If the operation is successful, the class driver increments CallNumber and calls the miniclass routine again. If the SRB fails, the class driver calls the miniclass routine again depending on the value of RetryFlags.

• TAPE_STATUS_CHECK_TEST_UNIT_READY

  This return value directs the tape class driver to create an SRB for the test unit ready command and to send the SRB to the device.

• TAPE_STATUS_CALLBACK

  This return value directs the tape class driver to increment CallNumber without sending an SRB to the device. This streamlines case statements that support several devices. For example, suppose that most of the tape devices supported by a particular miniclass driver require three SRBs to process a certain request. One device, however, requires only the first and third SRBs. For the unique device the tape miniclass driver can return TAPE_STATUS_CALLBACK to skip the second SRB, allowing the driver to use the same code to process the request for all the devices it supports.

• TAPE_STATUS_REQUIRES_CLEANING

  If a tape device supports cleaning notification in sense data rather than as an error, a tape miniclass driver's TapeMiniGetStatus routine returns this status to indicate to the tape class driver that the drive needs cleaning.

When the miniclass routine finishes processing a request--either successfully or with an error after retries are exhausted--it returns to the tape class driver with a TAPE_STATUS_XXX that indicates the success or failure of the request.