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scsi_pktalloc() requests the host adapter driver to allocate a command packet. For commands that have a data transfer associated with them, scsi_resalloc() should
be used.
ap is a pointer to a scsi_address structure. Allocator routines use it to determine the associated host adapter.
cmdlen is the required length for the SCSI command descriptor block. This block is allocated such that a kernel virtual address is established
in the pkt_cdbp field of the allocated scsi_pkt structure.
statuslen is the required length for the SCSI status completion block. The address of the allocated block is placed into the pkt_scbp field of the scsi_pkt structure.
dmatoken is a pointer to an implementation dependent object which defines the length, direction, and address of the data transfer associated with this SCSI packet (command). The dmatoken must be a pointer to a buf(9S) structure. If dmatoken is NULL, no DMA resources are required by this SCSI command, so none are allocated. Only one transfer direction is allowed per command. If there is an unexpected data transfer phase (either no data transfer phase expected, or
the wrong direction encountered), the command is terminated with the pkt_reason set to CMD_DMA_DERR. dmatoken provides
the information to determine if the transfer count is correct.
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 retry.
scsi_pktfree() frees the packet.
scsi_resfree() free all resources held by the packet and the packet itself.
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