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