generic: per-device coherent dma allocator

Currently x86_32, sh and cris-v32 provide per-device coherent dma
memory allocator.

However their implementation is nearly identical. Refactor out
common code to be reused by them.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/asm-generic/dma-coherent.h

@@ -0,0 +1,32 @@
+#ifndef DMA_COHERENT_H
+#define DMA_COHERENT_H
+
+#ifdef CONFIG_HAVE_GENERIC_DMA_COHERENT
+/*
+ * These two functions are only for dma allocator.
+ * Don't use them in device drivers.
+ */
+int dma_alloc_from_coherent(struct device *dev, ssize_t size,
+				       dma_addr_t *dma_handle, void **ret);
+int dma_release_from_coherent(struct device *dev, int order, void *vaddr);
+
+/*
+ * Standard interface
+ */
+#define ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY
+extern int
+dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
+			    dma_addr_t device_addr, size_t size, int flags);
+
+extern void
+dma_release_declared_memory(struct device *dev);
+
+extern void *
+dma_mark_declared_memory_occupied(struct device *dev,
+				  dma_addr_t device_addr, size_t size);
+#else
+#define dma_alloc_from_coherent(dev, size, handle, ret) (0)
+#define dma_release_from_coherent(dev, order, vaddr) (0)
+#endif
+
+#endif