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Copyright (c) 1994, Sun Microsystems, Inc.
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]
DDI_DMA_NEXTCOOKIE 9F "Sep 26, 1994"
NAME
ddi_dma_nextcookie - retrieve subsequent DMA cookie
SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>



void ddi_dma_nextcookie(ddi_dma_handle_t handle,
 ddi_dma_cookie_t *cookiep);
PARAMETERS
handle

The handle previously allocated by a call to ddi_dma_alloc_handle(9F).

cookiep

A pointer to a ddi_dma_cookie(9S) structure.

INTERFACE LEVEL

Solaris DDI specific (Solaris DDI).

DESCRIPTION

ddi_dma_nextcookie() retrieves subsequent DMA cookies for a DMA object. ddi_dma_nextcookie() fills in the ddi_dma_cookie(9S) structure pointed to by cookiep. The ddi_dma_cookie(9S) structure must be allocated prior to calling ddi_dma_nextcookie().

The DMA cookie count returned by ddi_dma_buf_bind_handle(9F), ddi_dma_addr_bind_handle(9F), or ddi_dma_getwin(9F) indicates the number of DMA cookies a DMA object consists of. If the resulting cookie count, N, is larger than 1, ddi_dma_nextcookie() must be called N-1 times to retrieve all DMA cookies.

CONTEXT

ddi_dma_nextcookie() can be called from user, kernel, or interrupt context.

EXAMPLES

Example 1 Process a scatter-gather list of I/O requests.

This example demonstrates the use of ddi_dma_nextcookie() to process a scatter-gather list of I/O requests.

/* setup scatter-gather list with multiple DMA cookies */
ddi_dma_cookie_t dmacookie;
uint_t ccount;
...

status = ddi_dma_buf_bind_handle(handle, bp, DDI_DMA_READ,
 NULL, NULL, &dmacookie, &ccount);

if (status == DDI_DMA_MAPPED) {

 /* program DMA engine with first cookie */

 while (--ccount > 0) {
 ddi_dma_nextcookie(handle, &dmacookie);
 /* program DMA engine with next cookie */
 }
}
...
SEE ALSO

ddi_dma_addr_bind_handle(9F), ddi_dma_alloc_handle(9F), ddi_dma_buf_bind_handle(9F), ddi_dma_unbind_handle(9F), ddi_dma_cookie(9S)

Writing Device Drivers