scsi_init_pkt(9F) Kernel Functions for Drivers scsi_init_pkt(9F)
scsi_init_pkt - prepare a complete SCSI packet
struct scsi_pkt *scsi_init_pkt(struct scsi_address *ap, struct scsi_pkt *pktp, struct buf *bp, int cmdlen, int statuslen, int privatelen,
int flags, int (*callback)(caddr_t), caddr_t arg);
Solaris DDI specific (Solaris DDI).
ap Pointer to a scsi_address(9S) structure.
pktp A pointer to a scsi_pkt(9S) structure.
bp Pointer to a buf(9S) structure.
cmdlen The required length for the SCSI command descriptor block (CDB) in bytes.
statuslen The required length for the SCSI status completion block (SCB) in bytes. Valid values are:
No status back.
Return SCSI status byte.
Return status information in a scsi_arq_status structure. This will include up to 20 bytes of sense data. Please refer
to scsi_arq_status(9S) for more information.
Same as preceding.
privatelen The required length for the pkt_private area.
flags Flags modifier.
callback A pointer to a callback function, NULL_FUNC, or SLEEP_FUNC.
arg The callback function argument.
Target drivers use scsi_init_pkt() to request the transport layer to allocate and initialize a packet for a SCSI command which possibly
includes a data transfer. If pktp is NULL, a new scsi_pkt(9S) is allocated using the HBA driver's packet allocator. The bp is a pointer to
a buf(9S) structure. If bp is non-NULL and contains a valid byte count, the buf(9S) structure is also set up for DMA transfer using the HBA
driver DMA resources allocator. When bp is allocated by scsi_alloc_consistent_buf(9F), the PKT_CONSISTENT bit must be set in the flags
argument to ensure proper operation. If privatelen is non-zero then additional space is allocated for the pkt_private area of the
scsi_pkt(9S). On return pkt_private points to this additional space. Otherwise pkt_private is a pointer that is typically used to store
the bp during execution of the command. In this case pkt_private is NULL on return.
The flags argument is a set of bit flags. Possible bits include:
"small and bold">PKT_CONSISTENT
This must be set if the DMA buffer was allocated using scsi_alloc_consistent_buf(9F). In this case, the HBA driver will guarantee that
the data transfer is properly synchronized before performing the target driver's command completion callback.
This may be set if the driver can accept a partial DMA mapping. If set, scsi_init_pkt() will allocate DMA resources with the
DDI_DMA_PARTIAL bit set in the dmar_flag element of the ddi_dma_req(9S) structure. The pkt_resid field of the scsi_pkt(9S) structure
may be returned with a non-zero value, which indicates the number of bytes for which scsi_init_pkt() was unable to allocate DMA
resources. In this case, a subsequent call to scsi_init_pkt() may be made for the same pktp and bp to adjust the DMA resources to the
next portion of the transfer. This sequence should be repeated until the pkt_resid field is returned with a zero value, which indicates
that with transport of this final portion the entire original request will have been satisfied.
When calling scsi_init_pkt() to move already-allocated DMA resources, the cmdlen, statuslen, and privatelen fields are ignored.
The last argument arg is supplied to the callback function when it is invoked.
callback indicates what the allocator routines should do when resources are not available:
NULL_FUNC Do not wait for resources. Return a NULL pointer.
SLEEP_FUNC Wait indefinitely for resources.
Other Values callback points to a function which is called when resources may have become available. callback must return either 0
(indicating that it attempted to allocate resources but again failed to do so), in which case it is put back on a list to
be called again later, or 1 indicating either success in allocating resources or indicating that it no longer cares for a
When allocating DMA resources, scsi_init_pkt() returns the scsi_pkt field pkt_resid as the number of residual bytes for which the system
was unable to allocate DMA resources. A pkt_resid of 0 means that all necessary DMA resources were allocated.
scsi_init_pkt() returns NULL if the packet or DMA resources could not be allocated. Otherwise, it returns a pointer to an initialized
scsi_pkt(9S). If pktp was not NULL the return value will be pktp on successful initialization of the packet.
If callback is SLEEP_FUNC, then this routine may only be called from user-level code. Otherwise, it may be called from either user or
interrupt level. The callback function may not block or call routines that block.
Example 1: Allocating a Packet Without DMA Resources Attached
To allocate a packet without DMA resources attached, use:
pkt = scsi_init_pkt(&devp->sd_address, NULL, NULL, CDB_GROUP1,
1, sizeof (struct my_pkt_private *), 0,
Example 2: Allocating a Packet With DMA Resources Attached
To allocate a packet with DMA resources attached use:
pkt = scsi_init_pkt(&devp->sd_address, NULL, bp, CDB_GROUP1,
sizeof(struct scsi_arq_status), 0, 0, NULL_FUNC, NULL);
Example 3: Attaching DMA Resources to a Preallocated Packet
To attach DMA resources to a preallocated packet, use:
pkt = scsi_init_pkt(&devp->sd_address, old_pkt, bp, 0,
0, 0, 0, sd_runout, (caddr_t) sd_unit);
Example 4: Allocating a Packet with Consistent DMA Resources Attached
Since the packet is already allocated, the cmdlen, statuslen and privatelen are 0. To allocate a packet with consistent DMA resources
bp = scsi_alloc_consistent_buf(&devp->sd_address, NULL,
SENSE_LENGTH, B_READ, SLEEP_FUNC, NULL);
pkt = scsi_init_pkt(&devp->sd_address, NULL, bp, CDB_GROUP0,
sizeof(struct scsi_arq_status), sizeof (struct my_pkt_private *),
PKT_CONSISTENT, SLEEP_FUNC, NULL);
Example 5: Allocating a Packet with Partial DMA Resources Attached
To allocate a packet with partial DMA resources attached, use:
my_pkt = scsi_init_pkt(&devp->sd_address, NULL, bp, CDB_GROUP0,
1, sizeof (struct buf *), PKT_DMA_PARTIAL,
scsi_alloc_consistent_buf(9F), scsi_destroy_pkt(9F), scsi_dmaget(9F), scsi_pktalloc(9F), buf(9S), ddi_dma_req(9S), scsi_address(9S),
Writing Device Drivers
If a DMA allocation request fails with DDI_DMA_NOMAPPING, the B_ERROR flag will be set in bp, and the b_error field will be set to EFAULT.
If a DMA allocation request fails with DDI_DMA_TOOBIG, the B_ERROR flag will be set in bp, and the b_error field will be set to EINVAL.
SunOS 5.10 15 Nov 2000 scsi_init_pkt(9F)