ARM: dma-mapping: introduce DMA_ERROR_CODE constant

Replace all uses of ~0 with DMA_ERROR_CODE, what should make the code
easier to read.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Tested-By: Subash Patel <subash.ramaswamy@linaro.org>

arch/arm/common/dmabounce.c

@@ -254,7 +254,7 @@ static inline dma_addr_t map_single(struct device *dev, void *ptr, size_t size,
 	if (buf == NULL) {
 		dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
 		       __func__, ptr);
-		return ~0;
+		return DMA_ERROR_CODE;
 	}
 
 	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
@@ -320,7 +320,7 @@ dma_addr_t __dma_map_page(struct device *dev, struct page *page,
 
 	ret = needs_bounce(dev, dma_addr, size);
 	if (ret < 0)
-		return ~0;
+		return DMA_ERROR_CODE;
 
 	if (ret == 0) {
 		__dma_page_cpu_to_dev(page, offset, size, dir);
@@ -329,7 +329,7 @@ dma_addr_t __dma_map_page(struct device *dev, struct page *page,
 
 	if (PageHighMem(page)) {
 		dev_err(dev, "DMA buffer bouncing of HIGHMEM pages is not supported\n");
-		return ~0;
+		return DMA_ERROR_CODE;
 	}
 
 	return map_single(dev, page_address(page) + offset, size, dir);

arch/arm/include/asm/dma-mapping.h

@@ -10,6 +10,8 @@
 #include <asm-generic/dma-coherent.h>
 #include <asm/memory.h>
 
+#define DMA_ERROR_CODE	(~0)
+
 #ifdef __arch_page_to_dma
 #error Please update to __arch_pfn_to_dma
 #endif
@@ -123,7 +125,7 @@ extern int dma_set_mask(struct device *, u64);
  */
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
-	return dma_addr == ~0;
+	return dma_addr == DMA_ERROR_CODE;
 }
 
 /*

arch/arm/mm/dma-mapping.c

@@ -342,7 +342,7 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
 	 */
 	gfp &= ~(__GFP_COMP);
 
-	*handle = ~0;
+	*handle = DMA_ERROR_CODE;
 	size = PAGE_ALIGN(size);
 
 	page = __dma_alloc_buffer(dev, size, gfp);