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 Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved
 The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
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 When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
 SCSI_ALLOC_CONSISTENT_BUF 9F "Jan 16, 2006"
 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);
 }




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

Writing Device Drivers