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tran_init_pkt, tran_destroy_pkt - SCSI HBA packet preparation and deallocation

#include <sys/scsi/scsi.h>

struct scsi_pkt *prefixtran_init_pkt(struct scsi_address *ap,
 struct scsi_pkt *pkt, struct buf *bp, int cmdlen,
 int statuslen, int tgtlen, intflags, int (*callback,
 caddr_t),caddr_t arg);

void prefixtran_destroy_pkt(struct scsi_address *ap,
 struct scsi_pkt *pkt);

illumos architecture specific (illumos DDI). ap pkt bp cmdlen statuslen tgtlen flags callback arg The tran_init_pkt() and tran_destroy_pkt() vectors in the scsi_hba_tran structure must be initialized during the HBA driver's attach(9E) to point to HBA entry points to be called when a target driver calls scsi_init_pkt(9F) and scsi_destroy_pkt(9F). tran_init_pkt() is the entry point into the HBA which is used to allocate and initialize a scsi_pkt structure on behalf of a SCSI target driver. If pkt is NULL, the HBA driver must use scsi_hba_pkt_alloc(9F) to allocate a new scsi_pkt structure.

If bp is non-NULL, the HBA driver must allocate appropriate DMA resources for the pkt, for example, through ddi_dma_buf_setup(9F) or ddi_dma_buf_bind_handle(9F).

If the PKT_CONSISTENT bit is set in flags, the buffer was allocated by scsi_alloc_consistent_buf(9F). For packets marked with PKT_CONSISTENT, the HBA driver must synchronize any cached data transfers before calling the target driver's command completion callback.

If the PKT_DMA_PARTIAL bit is set in flags, the HBA driver should set up partial data transfers, such as setting the DDI_DMA_PARTIAL bit in the flags argument if interfaces such as ddi_dma_buf_setup(9F) or ddi_dma_buf_bind_handle(9F) are used.

If only partial DMA resources are available, tran_init_pkt() must return in the pkt_resid field of pkt the number of bytes of DMA resources not allocated.

If both pkt and bp are non-NULL, if the PKT_DMA_PARTIAL bit is set in flags, and if DMA resources have already been allocated for the pkt with a previous call to tran_init_pkt() that returned a non-zero pkt_resid field, this request is to move the DMA resources for the subsequent piece of the transfer.

The contents of scsi_address(9S) pointed to by ap are copied into the pkt_address field of the scsi_pkt(9S) by scsi_hba_pkt_alloc(9F).

tgtlen is the length of the packet private area in the scsi_pkt structure to be allocated on behalf of the SCSI target driver.

statuslen is the required length for the SCSI status completion block. If the requested status length is greater than or equal to sizeof(struct scsi_arq_status) and the auto_rqsense capability has been set, automatic request sense (ARS) is enabled for this packet. If the status length is less than sizeof(struct scsi_arq_status), automatic request sense must be disabled for this pkt.

If the HBA driver is not capable of disabling ARQ on a per-packet basis and tran_init_pkt() is called with a statuslen that is less than sizeof(struct scsi_arq_status), the driver's tran_init_pkt routine should allocate at least sizeof(struct scsi_arq_status). If an ARS is needed, upon successful ARS done by the HBA driver, the driver must copy the sense data over and set STAT_ARQ_DONE in pkt_state.

cmdlen is the required length for the SCSI command descriptor block.

Note: tgtlen, statuslen, and cmdlen are used only when the HBA driver allocates the scsi_pkt(9S), in other words, when pkt is NULL.

callback indicates what the allocator routines should do when resources are not available: NULL_FUNC

SLEEP_FUNC tran_destroy_pkt() is the entry point into the HBA that must free all of the resources that were allocated to the scsi_pkt(9S) structure during tran_init_pkt(). tran_init_pkt() must return a pointer to a scsi_pkt(9S) structure on success, or NULL on failure.

If pkt is NULL on entry, and tran_init_pkt() allocated a packet through scsi_hba_pkt_alloc(9F) but was unable to allocate DMA resources, tran_init_pkt() must free the packet through scsi_hba_pkt_free(9F) before returning NULL.

attach (9E), tran_setup_pkt (9E), tran_sync_pkt (9E), biodone (9F), bioerror (9F), ddi_dma_buf_bind_handle (9F), ddi_dma_buf_setup (9F), kmem_cache_create (9F), scsi_alloc_consistent_buf (9F), scsi_destroy_pkt (9F), scsi_hba_attach (9F), scsi_hba_pkt_alloc (9F), scsi_hba_pkt_free (9F), scsi_init_pkt (9F), buf (9S), scsi_address (9S), scsi_hba_tran (9S), scsi_pkt (9S)

Writing Device Drivers

If a DMA allocation request fails with DDI_DMA_NOMAPPING, indicate the error by calling bioerror(9F) with bp and an error code of EFAULT.

If a DMA allocation request fails with DDI_DMA_TOOBIG, indicate the error by calling bioerror(9F) with bp and an error code of EINVAL.

For increased performance, an HBA driver may want to provide a cache for scsi_pkt(9S) allocation. This cache should be implemented by the HBA driver providing a tran_setup_pkt(9E) implementation. Implementing this cache by direct use of kmem_cache_create(9F) adds a compile-time dependency on scsi_pkt() size, which is illegal.