Sun Microsystems, Inc.
spacerspacer
spacer   www.sun.com docs.sun.com | | |  
spacer
black dot
   
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z
    
 
Kernel Functions for Driversddi_dma_nextwin(9F)


NAME

 ddi_dma_nextwin - get next DMA window

SYNOPSIS

 
#include <sys/ddi.h> 
#include <sys/sunddi.h>
int ddi_dma_nextwin(ddi_dma_handle_t handle, ddi_dma_win_t win, ddi_dma_win_t *nwin);

INTERFACE LEVEL

 

Solaris DDI specific (Solaris DDI).

PARAMETERS

 
handle
A DMA handle.
win
The current DMA window or NULL.
nwin
A pointer to the next DMA window to be filled in. If win is NULL, a pointer to the first window within the object is returned.

DESCRIPTION

 

ddi_dma_nextwin() shifts the current DMA window win within the object referred to by handle to the next DMA window nwin. If the current window is NULL, the first window within the object is returned. A DMA window is a portion of a DMA object or might be the entire object. A DMA window has system resources allocated to it and is prepared to accept data transfers. Examples of system resources are DVMA mapping resources and intermediate transfer buffer resources.

All DMA objects require a window. If the DMA window represents the whole DMA object it has system resources allocated for the entire data transfer. However, if the system is unable to setup the entire DMA object due to system resource limitations, the driver writer may allow the system to allocate system resources for less than the entire DMA object. This can be accomplished by specifying the DDI_DMA_PARTIAL flag as a parameter to ddi_dma_buf_setup(9F) or ddi_dma_addr_setup(9F) or as part of a ddi_dma_req(9S) structure in a call to ddi_dma_setup(9F).

Only the window that has resources allocated is valid per object at any one time. The currently valid window is the one that was most recently returned from ddi_dma_nextwin(). Furthermore, because a call to ddi_dma_nextwin() will reallocate system resources to the new window, the previous window will become invalid. It is a severe error to call ddi_dma_nextwin() before any transfers into the current window are complete.

ddi_dma_nextwin() takes care of underlying memory synchronizations required to shift the window. However, if you want to access the data before or after moving the window, further synchronizations using ddi_dma_sync(9F) are required.

RETURN VALUES

 

ddi_dma_nextwin() returns:

DDI_SUCCESS
Successfully filled in the next window pointer.
DDI_DMA_DONE
There is no next window. The current window is the final window within the specified object.
DDI_DMA_STALE
win does not refer to the currently active window.

CONTEXT

 

ddi_dma_nextwin() can be called from user or interrupt context.

EXAMPLES

 

For an example see ddi_dma_segtocookie(9F).

SEE ALSO

 

ddi_dma_addr_setup(9F), ddi_dma_buf_setup(9F), ddi_dma_nextseg(9F), ddi_dma_segtocookie(9F), ddi_dma_sync(9F), ddi_dma_req(9S)

Writing Device Drivers


SunOS 5.9Go To TopLast Changed 12 Oct 1992

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