'\" te
.\"  Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved
.TH scsi_alloc_consistent_buf 9F "16 Jan 2006" "SunOS 5.11" "Kernel Functions for Drivers"
.SH NAME
scsi_alloc_consistent_buf \- allocate an I/O buffer for SCSI DMA
.SH SYNOPSIS
.LP
.nf
#include <sys/scsi/scsi.h>

\fBstruct buf *\fR\fBscsi_alloc_consistent_buf\fR(\fBstructscsi_address*\fR\fIap\fR, 
     \fBstruct buf *\fR\fIbp\fR, \fBsize_t\fR \fIdatalen\fR, \fBuint_t\fR \fIbflags\fR, 
     \fBint (*\fR\fIcallback\fR)(caddr_t), \fBcaddr_t\fR \fIarg\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Solaris DDI specific (Solaris DDI).
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIap\fR\fR
.ad
.RS 12n
.rt  
Pointer to the \fBscsi_address\fR(9S) structure.
.RE

.sp
.ne 2
.mk
.na
\fB\fIbp\fR\fR
.ad
.RS 12n
.rt  
Pointer to the \fBbuf\fR(9S) structure.
.RE

.sp
.ne 2
.mk
.na
\fB\fIdatalen\fR\fR
.ad
.RS 12n
.rt  
Number of bytes for the data buffer.
.RE

.sp
.ne 2
.mk
.na
\fB\fIbflags\fR\fR
.ad
.RS 12n
.rt  
Flags setting for the allocated buffer header. This should either be \fBB_READ\fR or \fBB_WRITE\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIcallback\fR\fR
.ad
.RS 12n
.rt  
A pointer to a callback function, \fBNULL_FUNC\fR or \fBSLEEP_FUNC\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIarg\fR\fR
.ad
.RS 12n
.rt  
The callback function argument.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBscsi_alloc_consistent_buf()\fR function returns allocates a buffer header and the associated data buffer for direct memory access (DMA) transfer. This buffer is allocated from the \fBiobp\fR space, which is considered consistent memory. For more details, see \fBddi_dma_mem_alloc\fR(9F) and \fBddi_dma_sync\fR(9F).
.sp
.LP
For buffers allocated via \fBscsi_alloc_consistent_buf()\fR, and marked with the \fBPKT_CONSISTENT\fR flag via \fBscsi_init_pkt\fR(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.
.sp
.LP
If \fIbp\fR is \fINULL\fR, a new buffer header will be allocated using \fBgetrbuf\fR(9F). In addition, if \fIdatalen\fR is non-zero, a new buffer will be allocated using \fBddi_dma_mem_alloc\fR(9F).
.sp
.LP
\fIcallback\fR indicates what the allocator routines should do when direct memory access \fB(DMA)\fR resources are not available; the valid values are:
.sp
.ne 2
.mk
.na
\fB\fBNULL_FUNC\fR\fR
.ad
.RS 16n
.rt  
Do not wait for resources. Return a \fINULL\fR pointer.
.RE

.sp
.ne 2
.mk
.na
\fB\fBSLEEP_FUNC\fR\fR
.ad
.RS 16n
.rt  
Wait indefinitely for resources.
.RE

.sp
.ne 2
.mk
.na
\fBOther Values\fR
.ad
.RS 16n
.rt  
\fIcallback\fR points to a function that is called when resources may become available. \fIcallback\fR must return either \fB0\fR (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 \fB1\fR indicating either success in allocating resources or indicating that it no longer cares for a retry. The last argument \fIarg\fR is supplied to the \fIcallback\fR function when it is invoked.
.RE

.SH RETURN VALUES
.sp
.LP
The \fBscsi_alloc_consistent_buf()\fR function returns a pointer to a \fBbuf\fR(9S) structure on success. It returns \fBNULL\fR if resources are not available even if \fIwaitfunc\fR was not \fBSLEEP_FUNC\fR.
.SH CONTEXT
.sp
.LP
If \fIcallback\fR is \fBSLEEP_FUNC\fR, then this routine may be called only from user-level code. Otherwise, it may be called fromuser, interrupt, or kernel context. The \fIcallback\fR function may not block or call routines that block.
.SH EXAMPLES
.LP
\fBExample 1 \fRAllocate a request sense packet with consistent DMA resources attached.
.sp
.in +2
.nf
   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);
.fi
.in -2

.LP
\fBExample 2 \fRAllocate an inquiry packet with consistent DMA resources attached.
.sp
.in +2
.nf
    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);
    }
.fi
.in -2

.SH SEE ALSO
.sp
.LP
\fBddi_dma_mem_alloc\fR(9F), \fBddi_dma_sync\fR(9F), \fBgetrbuf\fR(9F), \fBscsi_destroy_pkt\fR(9F), \fBscsi_init_pkt\fR(9F), \fBscsi_free_consistent_buf\fR(9F), \fBbuf\fR(9S), \fBscsi_address\fR(9S)
.sp
.LP
\fIWriting Device Drivers for Oracle Solaris 11.2\fR