ddi_dma_nextwin(9F) Kernel Functions for Drivers ddi_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
This interface is obsolete. ddi_dma_getwin(9F) should be used instead.
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_set-
up(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 win-
dow, 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).
ATTRIBUTES
See attributes(5) for a description of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Stability Level |Obsolete |
+-----------------------------+-----------------------------+
SEE ALSO
attributes(5), ddi_dma_addr_setup(9F), ddi_dma_buf_setup(9F), ddi_dma_getwin(9F), ddi_dma_nextseg(9F), ddi_dma_segtocookie(9F),
ddi_dma_sync(9F), ddi_dma_req(9S)
Writing Device Drivers
SunOS 5.10 27 Sep 2002 ddi_dma_nextwin(9F)