Tribblix: manual page: scsi_alloc_consistent

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

illumos DDI specific (illumos 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);
}