dma-direct: rename dma_noop to dma_direct

The trivial direct mapping implementation already does a virtual to
physical translation which isn't strictly a noop, and will soon learn
to do non-direct but linear physical to dma translations through the
device offset and a few small tricks.  Rename it to a better fitting
name.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Vladimir Murzin <[email protected]>

lib/dma-direct.c

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	lib/dma-noop.c
+ *
+ * DMA operations that map to physical addresses without flushing memory.
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+#include <linux/pfn.h>
+
+static void *dma_direct_alloc(struct device *dev, size_t size,
+		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
+{
+	void *ret;
+
+	ret = (void *)__get_free_pages(gfp, get_order(size));
+	if (ret)
+		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
+
+	return ret;
+}
+
+static void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
+		dma_addr_t dma_addr, unsigned long attrs)
+{
+	free_pages((unsigned long)cpu_addr, get_order(size));
+}
+
+static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		unsigned long attrs)
+{
+	return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
+}
+
+static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+	int i;
+	struct scatterlist *sg;
+
+	for_each_sg(sgl, sg, nents, i) {
+		dma_addr_t offset = PFN_PHYS(dev->dma_pfn_offset);
+		void *va;
+
+		BUG_ON(!sg_page(sg));
+		va = sg_virt(sg);
+		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va) - offset;
+		sg_dma_len(sg) = sg->length;
+	}
+
+	return nents;
+}
+
+const struct dma_map_ops dma_direct_ops = {
+	.alloc			= dma_direct_alloc,
+	.free			= dma_direct_free,
+	.map_page		= dma_direct_map_page,
+	.map_sg			= dma_direct_map_sg,
+};
+EXPORT_SYMBOL(dma_direct_ops);