SCSI_ALLOC_CONSISTENT_BUF(9F) Kernel Functions for Drivers


NAME


scsi_alloc_consistent_buf - allocate an I/O buffer for SCSI DMA

SYNOPSIS


#include <sys/scsi/scsi.h>


struct buf *scsi_alloc_consistent_buf(structscsi_address*ap,
struct buf *bp, size_t datalen, uint_t bflags,
int (*callback)(caddr_t), caddr_t arg);


INTERFACE LEVEL


Solaris DDI specific (Solaris DDI).

PARAMETERS


ap
Pointer to the scsi_address(9S) structure.


bp
Pointer to the buf(9S) structure.


datalen
Number of bytes for the data buffer.


bflags
Flags setting for the allocated buffer header. This should
either be B_READ or B_WRITE.


callback
A pointer to a callback function, NULL_FUNC or SLEEP_FUNC.


arg
The callback function argument.


DESCRIPTION


The scsi_alloc_consistent_buf() function returns allocates a buffer
header and the associated data buffer for direct memory access (DMA)
transfer. This buffer is allocated from the iobp space, which is
considered consistent memory. For more details, see ddi_dma_mem_alloc(9F)
and ddi_dma_sync(9F).


For buffers allocated via scsi_alloc_consistent_buf(), and marked with
the PKT_CONSISTENT flag via scsi_init_pkt(9F), the HBA driver must ensure
that the data transfer for the command is correctly synchronized before
the target driver's command completion callback is performed.


If bp is NULL, a new buffer header will be allocated using getrbuf(9F).
In addition, if datalen is non-zero, a new buffer will be allocated using
ddi_dma_mem_alloc(9F).


callback indicates what the allocator routines should do when direct
memory access (DMA) resources are not available; the valid values are:

NULL_FUNC
Do not wait for resources. Return a NULL pointer.


SLEEP_FUNC
Wait indefinitely for resources.


Other Values
callback points to a function that is called when
resources may become available. callback must return
either 0 (indicating that it attempted to allocate
resources but 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. The last argument arg is
supplied to the callback function when it is invoked.


RETURN VALUES


The scsi_alloc_consistent_buf() function returns a pointer to a buf(9S)
structure on success. It returns NULL if resources are not available even
if waitfunc was not SLEEP_FUNC.

CONTEXT


If callback is SLEEP_FUNC, then this routine may be called only from
user-level code. Otherwise, it may be called fromuser, interrupt, or
kernel context. The callback function may not block or call routines that
block.

EXAMPLES


Example 1: Allocate a request sense packet with consistent DMA resources


attached.

bp = scsi_alloc_consistent_buf(&devp->sd_address, NULL,
SENSE_LENGTH, B_READ, SLEEP_FUNC, NULL);
rqpkt = scsi_init_pkt(&devp->sd_address,
NULL, bp, CDB_GROUP0, 1, 0,
PKT_CONSISTENT, SLEEP_FUNC, NULL);


Example 2: Allocate an inquiry packet with consistent DMA resources


attached.

bp = scsi_alloc_consistent_buf(&devp->sd_address, NULL,
SUN_INQSIZE, B_READ, canwait, NULL);
if (bp) {
pkt = scsi_init_pkt(&devp->sd_address, NULL, bp,
CDB_GROUP0, 1, PP_LEN, PKT_CONSISTENT,
canwait, NULL);
}


SEE ALSO


ddi_dma_mem_alloc(9F), ddi_dma_sync(9F), getrbuf(9F),
scsi_destroy_pkt(9F), scsi_init_pkt(9F), scsi_free_consistent_buf(9F),
buf(9S), scsi_address(9S)


Writing Device Drivers


January 16, 2006 SCSI_ALLOC_CONSISTENT_BUF(9F)