Specifications

Data Structures
1.15 SCSI Class Driver Request Packet (SCDRP)
Table 1–17 (Cont.) Contents of SCSI Class Driver Request Packet
Field Name Contents
IRP$V_PHYSIO Physical-I/O function
IRP$V_TERMIO Terminal I/O (for priority increment calculation)
IRP$V_MBXIO Mailbox-I/O function
IRP$V_EXTEND An extended IRP is linked to this IRP
IRP$V_FILACP File ACP I/O
IRP$V_MVIRP Mount-verification I/O function
IRP$V_SRVIO Server-type I/O
IRP$V_KEY Encrypted function (encryption key address at
IRP$L_KEYDESC)
SCDRP$L_SVAPTE For a direct-I/O transfer, virtual address of the first page-table entry (PTE) of
the I/O transfer buffer. This address is originally written to IRP$L_SVAPTE
by the FDT routine that locks process pages. For a buffered-I/O transfer,
address of a buffer in system address space. This address is originally
written to IRP$L_SVAPTE by the class driver FDT routine that allocates the
buffer.
The class driver’s start-I/O routine copies the address from the IRP to this
field.
SCDRP$W_BOFF For a direct-I/O transfer, byte offset into the first page of the buffer; for
a buffered-I/O transfer, number of bytes to be charged to the process
requesting the transfer. FDT routines calculate this value and write it
to IRP$W_BOFF.
The class driver’s start-I/O routine copies the value from the IRP to this
field.
SCDRP$L_BCNT Byte count of the I/O transfer. Class driver FDT routines calculate this value
and write it to IRP$L_BCNT. The class driver’s start-I/O routine copies the
value from the IRP to this field.
SCDRP$L_MEDIA Address of the media.
SCDRP$L_ABCNT Accumulated count of bytes transferred. The SCSI class driver maintains
this field to accomplish segmented transfers.
SCDRP$L_SAVD_RTN Saved return address from Level 1 JSB.
SCDRP$L_MSG_BUF Address of allocated MSCP buffer.
SCDRP$L_RSPID Allocated request ID.
SCDRP$L_CDT Address of the SCSI connection descriptor table (SCDT). When the SCSI
class driver’s unit initialization routine invokes the SPI$CONNECT macro,
the macro returns the address of the SCDT describing the connection
it established to the SCSI port. The class driver stores that address in
SCDRP$L_CDT.
SCDRP$L_RWCPTR RWAITCNT pointer.
SCDRP$L_IRP Address of I/O request block. The SCSI class driver copies the address of the
IRP to this field.
SCDRP$L_SVA_USER System virtual address of a process buffer as mapped in system space (S0
space). The SCSI port driver initializes this field as the result of a class
driver call to SPI$MAP_BUFFER.
SCDRP$L_CMD_BUF Address of the port command buffer. The SCSI class driver initializes this
field with the address returned from a call to SPI$ALLOCATE_COMMAND_
BUFFER.
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