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Kernel Functions for Driversddi_dma_getwin(9F)


NAME

 ddi_dma_getwin - activate a new DMA window

SYNOPSIS

 
#include <sys/ddi.h> 
#include <sys/sunddi.h> 
int ddi_dma_getwin(ddi_dma_handle_t handle, uint_t win, off_t *offp, size_t *lenp, ddi_dma_cookie_t *cookiep, uint_t *ccountp);

INTERFACE LEVEL

 

Solaris DDI specific (Solaris DDI).

PARAMETERS

 
handle
The DMA handle previously allocated by a call to ddi_dma_alloc_handle(9F).
win
Number of the window to activate.
offp
Pointer to an offset. Upon a successful return, offp will contain the new offset indicating the beginning of the window within the object.
lenp
Upon a successful return, lenp will contain the size, in bytes, of the current window.
cookiep
A pointer to the first ddi_dma_cookie(9S) structure.
ccountp
Upon a successful return, ccountp will contain the number of cookies for this DMA window.

DESCRIPTION

 

ddi_dma_getwin() activates a new DMA window. If a DMA resource allocation request returns DDI_DMA_PARTIAL_MAP indicating that resources for less than the entire object were allocated, the current DMA window can be changed by a call to ddi_dma_getwin().

The caller must first determine the number of DMA windows, N, using ddi_dma_numwin(9F). ddi_dma_getwin() takes a DMA window number from the range [0..N-1] as the parameter win and makes it the current DMA window.

ddi_dma_getwin() fills in the first DMA cookie pointed to by cookiep with the appropriate address, length, and bus type. *ccountp is set to the number of DMA cookies representing this DMA object. Subsequent DMA cookies must be retrieved using ddi_dma_nextcookie(9F).

ddi_dma_getwin() takes care of underlying resource synchronizations required to shift the window. However accessing the data prior to or after moving the window requires further synchronization steps using ddi_dma_sync(9F).

ddi_dma_getwin() is normally called from an interrupt routine. The first invocation of the DMA engine is done from the driver. All subsequent invocations of the DMA engine are done from the interrupt routine. The interrupt routine checks to see if the request has been completed. If it has, the interrupt routine returns without invoking another DMA transfer. Otherwise, it calls ddi_dma_getwin() to shift the current window and start another DMA transfer.

RETURN VALUES

 

ddi_dma_getwin() returns:

DDI_SUCCESS
Resources for the specified DMA window are allocated.
DDI_FAILURE
win is not a valid window index.

CONTEXT

 

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

SEE ALSO

 

ddi_dma_addr_bind_handle(9F), ddi_dma_alloc_handle(9F), ddi_dma_buf_bind_handle(9F), ddi_dma_nextcookie(9F), ddi_dma_numwin(9F), ddi_dma_sync(9F), ddi_dma_unbind_handle(9F), ddi_dma_cookie(9S)

Writing Device Drivers


SunOS 5.9Go To TopLast Changed 15 Nov 1996

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.