dma-mapping: move dma_common_{mmap,get_sgtable} out of mapping.c

Add a new file that contains helpers for misc DMA ops, which is only
built when CONFIG_DMA_OPS is set.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

kernel/dma/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_HAS_DMA)			+= mapping.o direct.o
+obj-$(CONFIG_DMA_OPS)			+= ops_helpers.o
 obj-$(CONFIG_DMA_OPS)			+= dummy.o
 obj-$(CONFIG_DMA_CMA)			+= contiguous.o
 obj-$(CONFIG_DMA_DECLARE_COHERENT)	+= coherent.o

kernel/dma/mapping.c

@@ -8,7 +8,7 @@
 #include <linux/memblock.h> /* for max_pfn */
 #include <linux/acpi.h>
 #include <linux/dma-direct.h>
-#include <linux/dma-noncoherent.h>
+#include <linux/dma-mapping.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/of_device.h>
@@ -295,22 +295,6 @@ void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 }
 EXPORT_SYMBOL(dma_sync_sg_for_device);
 
-/*
- * Create scatter-list for the already allocated DMA buffer.
- */
-int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
-		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		 unsigned long attrs)
-{
-	struct page *page = virt_to_page(cpu_addr);
-	int ret;
-
-	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
-	if (!ret)
-		sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
-	return ret;
-}
-
 /*
  * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
  * that the intention is to allow exporting memory allocated via the
@@ -358,35 +342,6 @@ pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs)
 }
 #endif /* CONFIG_MMU */
 
-/*
- * Create userspace mapping for the DMA-coherent memory.
- */
-int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
-		void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		unsigned long attrs)
-{
-#ifdef CONFIG_MMU
-	unsigned long user_count = vma_pages(vma);
-	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	unsigned long off = vma->vm_pgoff;
-	int ret = -ENXIO;
-
-	vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
-
-	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
-		return ret;
-
-	if (off >= count || user_count > count - off)
-		return -ENXIO;
-
-	return remap_pfn_range(vma, vma->vm_start,
-			page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
-			user_count << PAGE_SHIFT, vma->vm_page_prot);
-#else
-	return -ENXIO;
-#endif /* CONFIG_MMU */
-}
-
 /**
  * dma_can_mmap - check if a given device supports dma_mmap_*
  * @dev: device to check

kernel/dma/ops_helpers.c

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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-noncoherent.h>
+
+/*
+ * Create scatter-list for the already allocated DMA buffer.
+ */
+int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
+		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
+		 unsigned long attrs)
+{
+	struct page *page = virt_to_page(cpu_addr);
+	int ret;
+
+	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+	if (!ret)
+		sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+	return ret;
+}
+
+/*
+ * Create userspace mapping for the DMA-coherent memory.
+ */
+int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
+		void *cpu_addr, dma_addr_t dma_addr, size_t size,
+		unsigned long attrs)
+{
+#ifdef CONFIG_MMU
+	unsigned long user_count = vma_pages(vma);
+	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	unsigned long off = vma->vm_pgoff;
+	int ret = -ENXIO;
+
+	vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
+
+	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
+		return ret;
+
+	if (off >= count || user_count > count - off)
+		return -ENXIO;
+
+	return remap_pfn_range(vma, vma->vm_start,
+			page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
+			user_count << PAGE_SHIFT, vma->vm_page_prot);
+#else
+	return -ENXIO;
+#endif /* CONFIG_MMU */
+}