dma-mapping: merge <linux/dma-contiguous.h> into <linux/dma-map-ops.h>

Merge dma-contiguous.h into dma-map-ops.h, after removing the comment
describing the contiguous allocator into kernel/dma/contigous.c.

Signed-off-by: Christoph Hellwig <hch@lst.de>

5 files changed, 31 insertions, 5 deletions

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 647996702bc9..c99de4a21458 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -118,7 +118,7 @@ config DMA_CMA
 	  You can disable CMA by specifying "cma=0" on the kernel's command
 	  line.
 
-	  For more information see <include/linux/dma-contiguous.h>.
+	  For more information see <kernel/dma/contiguous.c>.
 	  If unsure, say "n".
 
 if  DMA_CMA
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index bf05ec2256e1..6bfb763fff6f 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -5,6 +5,34 @@
  * Written by:
  *	Marek Szyprowski <m.szyprowski@samsung.com>
  *	Michal Nazarewicz <mina86@mina86.com>
+ *
+ * Contiguous Memory Allocator
+ *
+ *   The Contiguous Memory Allocator (CMA) makes it possible to
+ *   allocate big contiguous chunks of memory after the system has
+ *   booted.
+ *
+ * Why is it needed?
+ *
+ *   Various devices on embedded systems have no scatter-getter and/or
+ *   IO map support and require contiguous blocks of memory to
+ *   operate.  They include devices such as cameras, hardware video
+ *   coders, etc.
+ *
+ *   Such devices often require big memory buffers (a full HD frame
+ *   is, for instance, more then 2 mega pixels large, i.e. more than 6
+ *   MB of memory), which makes mechanisms such as kmalloc() or
+ *   alloc_page() ineffective.
+ *
+ *   At the same time, a solution where a big memory region is
+ *   reserved for a device is suboptimal since often more memory is
+ *   reserved then strictly required and, moreover, the memory is
+ *   inaccessible to page system even if device drivers don't use it.
+ *
+ *   CMA tries to solve this issue by operating on memory regions
+ *   where only movable pages can be allocated from.  This way, kernel
+ *   can use the memory for pagecache and when device driver requests
+ *   it, allocated pages can be migrated.
  */
 
 #define pr_fmt(fmt) "cma: " fmt
@@ -21,7 +49,7 @@
 #include <linux/memblock.h>
 #include <linux/err.h>
 #include <linux/sizes.h>
-#include <linux/dma-contiguous.h>
+#include <linux/dma-map-ops.h>
 #include <linux/cma.h>
 
 #ifdef CONFIG_CMA_SIZE_MBYTES
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 8cf5689a8c40..87697c86f0b8 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -10,7 +10,6 @@
 #include <linux/dma-direct.h>
 #include <linux/dma-map-ops.h>
 #include <linux/scatterlist.h>
-#include <linux/dma-contiguous.h>
 #include <linux/pfn.h>
 #include <linux/vmalloc.h>
 #include <linux/set_memory.h>
diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
index 60d7b6cdfd8d..bc80fd2648bc 100644
--- a/kernel/dma/ops_helpers.c
+++ b/kernel/dma/ops_helpers.c
@@ -3,7 +3,6 @@
  * Helpers for DMA ops implementations.  These generally rely on the fact that
  * the allocated memory contains normal pages in the direct kernel mapping.
  */
-#include <linux/dma-contiguous.h>
 #include <linux/dma-map-ops.h>
 #include <linux/dma-noncoherent.h>
 
diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index fe11643ff9cc..c9fb5c3d8bd0 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -5,7 +5,7 @@
  */
 #include <linux/cma.h>
 #include <linux/debugfs.h>
-#include <linux/dma-contiguous.h>
+#include <linux/dma-map-ops.h>
 #include <linux/dma-direct.h>
 #include <linux/dma-noncoherent.h>
 #include <linux/init.h>