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)

2 files changed, 32 insertions, 8 deletions

diff --git a/sys/alpha/alpha/busdma_machdep.c b/sys/alpha/alpha/busdma_machdep.c
index 9de3342..3fcbc30 100644
--- a/sys/alpha/alpha/busdma_machdep.c
+++ b/sys/alpha/alpha/busdma_machdep.c
@@ -350,14 +350,18 @@ bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
  * A dmamap to for use with dmamap_load is also allocated.
  */
 int
-bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
-		 bus_dmamap_t *mapp)
+bus_dmamem_alloc_size(bus_dma_tag_t dmat, void** vaddr, int flags,
+		      bus_dmamap_t *mapp, bus_size_t size)
 {
+
+	if (size > dmat->maxsize)
+		return (ENOMEM);
+
 	/* If we succeed, no mapping/bouncing will be required */
 	*mapp = &nobounce_dmamap;
 
-	if ((dmat->maxsize <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem)) {
-		*vaddr = malloc(dmat->maxsize, M_DEVBUF,
+	if ((size <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem)) {
+		*vaddr = malloc(size, M_DEVBUF,
 				(flags & BUS_DMA_NOWAIT) ? M_NOWAIT : 0);
 	} else {
 		/*
@@ -365,7 +369,7 @@ bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
 		 *     and handles multi-seg allocations.  Nobody is doing
 		 *     multi-seg allocations yet though.
 		 */
-		*vaddr = contigmalloc(dmat->maxsize, M_DEVBUF,
+		*vaddr = contigmalloc(size, M_DEVBUF,
 		    (flags & BUS_DMA_NOWAIT) ? M_NOWAIT : 0,
 		    0ul, dmat->lowaddr, dmat->alignment? dmat->alignment : 1ul,
 		    dmat->boundary);
@@ -375,12 +379,20 @@ bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
 	return (0);
 }
 
+int
+bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
+		 bus_dmamap_t *mapp)
+{
+	return (bus_dmamem_alloc_size(dmat, vaddr, flags, mapp, dmat->maxsize));
+}
+
 /*
  * Free a piece of memory and it's allociated dmamap, that was allocated
  * via bus_dmamem_alloc.
  */
 void
-bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
+bus_dmamem_free_size(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map,
+		     bus_size_t size)
 {
 	/*
 	 * dmamem does not need to be bounced, so the map should be
@@ -388,10 +400,16 @@ bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
 	 */
 	if (map != &nobounce_dmamap)
 		panic("bus_dmamem_free: Invalid map freed\n");
-	if ((dmat->maxsize <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem))
+	if ((size <= PAGE_SIZE) && dmat->lowaddr >= ptoa(Maxmem))
 		free(vaddr, M_DEVBUF);
 	else
-		contigfree(vaddr, dmat->maxsize, M_DEVBUF);
+		contigfree(vaddr, size, M_DEVBUF);
+}
+
+void
+bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
+{
+	bus_dmamem_free_size(dmat, vaddr, map, dmat->maxsize);
 }
 
 #define BUS_DMAMAP_NSEGS ((BUS_SPACE_MAXSIZE / PAGE_SIZE) + 1)
diff --git a/sys/alpha/include/bus.h b/sys/alpha/include/bus.h
index 784eda3..3a87d1a 100644
--- a/sys/alpha/include/bus.h
+++ b/sys/alpha/include/bus.h
@@ -571,6 +571,9 @@ 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);
 
@@ -578,6 +581,9 @@ 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);
 
 /*