Specifications

Data Structures
1.15 SCSI Class Driver Request Packet (SCDRP)
Table 1–17 Contents of SCSI Class Driver Request Packet
Field Name Contents
SCDRP$L_FQFL Fork queue forward link. This field points to the next entry in the SCSI
adapter’s command buffer wait queue (ADP$L_BVPWAITFL), map register
wait queue (ADP$L_MRQFL), port wait queue (SPDT$L_PORT_WQFL), or
system fork queue.
SCDRP$L_FQBL Fork queue backward link. This field points to the previous entry in the
SCSI adapter’s command buffer wait queue (ADP$L_BVPWAITFL), map
register wait queue (ADP$L_MRQFL), port wait queue (SPDT$L_PORT_
WQFL), or system fork queue.
SCDRP$W_SCDRPSIZE Size of SCDRP. A SCSI class driver, after allocating sufficient nonpaged pool
for the SCDRP, writes the constant SCDRP$C_LENGTH into this field.
SCDRP$B_CD_TYPE Class driver type. This field is currently unused.
SCDRP$B_FLCK Index of the fork lock that synchronizes access to this SCDRP at fork level.
A SCSI class driver, after allocating sufficient nonpaged pool for the SCDRP,
copies to this field the value of UCB$B_FLCK. All devices controlled by a
single SCSI adapter and actively competing for shared adapter resources
must specify the same value for this field.
SCDRP$L_FPC Address of instruction at which processing resumes when SCSI adapter
resources become available to satisfy a request stalled in an adapter resource
wait queue.
SCDRP$L_FR3 Value of R3 when the request is stalled to wait for SCSI adapter resources.
When the request is satisfied, this value is restored to R3 before the driver
resumes execution at SCDRP$L_FPC.
SCDRP$L_FR4 Value of R4 when the request is stalled to wait for SCSI adapter resources.
When the request is satisfied, this value is restored to R4 before the driver
resumes execution art SCDRP$L_FPC.
SCDRP$L_PORT_UCB SCSI adapter’s UCB address. The SCSI port driver reads and writes this
field in order to manage ownership of the SCSI port across bus reselection.
SCDRP$L_UCB SCSI device’s UCB address. The SCSI class driver initializes this field to
indicate that the SCDRP is active.
SCDRP$W_FUNC I/O function code that identifies the function to be performed for the I/O
request. The SCSI class driver’s start-I/O routine copies the contents of
IRP$W_FUNC to this field.
SCDRP$W_STS Status of I/O request. The SCSI class driver’s start-I/O routine copies the
contents of IRP$W_STS to this field.
Bits in the SCDRP$W_STS field correspond to the bits in the IRP$W_STS
field that describe the type of I/O function, as follows:
IRP$V_BUFIO Buffered-I/O function
IRP$V_FUNC Read function
IRP$V_PAGIO Paging-I/O function
IRP$V_COMPLX Complex-buffered-I/O function
IRP$V_VIRTUAL Virtual-I/O function
IRP$V_CHAINED Chained-buffered-I/O function
IRP$V_SWAPIO Swapping-I/O function
IRP$V_DIAGBUF Diagnostic buffer present
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