Implement bus_dmamem_alloc_size() and bus_dmamem_free_size() as

counterparts to bus_dmamem_alloc() and bus_dmamem_free().  This allows
the caller to specify the size of the allocation instead of it defaulting
to the max_size field of the busdma tag.

This is intended to aid in converting drivers to busdma.  Lots of
hardware cannot understand scatter/gather lists, which forces the
driver to copy the i/o buffers to a single contiguous region
before sending it to the hardware.  Without these new methods, this
would require a new busdma tag for each operation, or a complex
internal allocator/cache for each driver.

Allocations greater than PAGE_SIZE are rounded up to the next
PAGE_SIZE by contigmalloc(), so this is not suitable for multiple
static allocations that would be better served by a single
fixed-length subdivided allocation.

Reviewed by:	jake (sparc64)

1 files changed, 6 insertions, 0 deletions

diff --git a/sys/sys/bus_dma.h b/sys/sys/bus_dma.h
index 6790731..4a1740d 100644
--- a/sys/sys/bus_dma.h
+++ b/sys/sys/bus_dma.h
@@ -180,6 +180,9 @@ int bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map);
  * bus device space based on the constraints lited in the dma tag.
  * A dmamap to for use with dmamap_load is also allocated.
  */
+int bus_dmamem_alloc_size(bus_dma_tag_t dmat, void** vaddr, int flags,
+			  bus_dmamap_t *mapp, bus_size_t size);
+
 int bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
 		     bus_dmamap_t *mapp);
 
@@ -187,6 +190,9 @@ int bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
  * Free a piece of memory and it's allociated dmamap, that was allocated
  * via bus_dmamem_alloc.
  */
+void bus_dmamem_free_size(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map,
+			  bus_size_t size);
+
 void bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map);
 
 /*