ddi_dma_nextwin(9F) Kernel Functions for Drivers ddi_dma_nextwin(9F)NAMEddi_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This interface is obsolete.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
The ddi_dma_nextwin() function 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 pre‐
pared 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 com‐
plete.
The ddi_dma_nextwin() function takes care of underlying memory synchro‐
nizations 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
The ddi_dma_nextwin() function 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
The ddi_dma_nextwin() function can be called from user, interrupt, or
kernel 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 ALSOattributes(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 16 Jan 2006 ddi_dma_nextwin(9F)
