[Xen-devel] [PATCH v7 1/9] dma: Provide simple noop dma ops

[Andy Lutomirski <luto@xxxxxxxxxx>]

From: Christian Borntraeger <borntraeger@xxxxxxxxxx>

We are going to require dma_ops for several common drivers, even for
systems that do have an identity mapping. Lets provide some minimal
no-op dma_ops that can be used for that purpose.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 include/linux/dma-mapping.h |  2 ++
 lib/Makefile                |  1 +
 lib/dma-noop.c              | 75 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+)
 create mode 100644 lib/dma-noop.c

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 75857cda38e9..c0b27ff2c784 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -70,6 +70,8 @@ struct dma_map_ops {
        int is_phys;
 };
 
+extern struct dma_map_ops dma_noop_ops;
+
 #define DMA_BIT_MASK(n)        (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
 
 #define DMA_MASK_NONE  0x0ULL
diff --git a/lib/Makefile b/lib/Makefile
index a7c26a41a738..a572b86a1b1d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -18,6 +18,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
+lib-$(CONFIG_HAS_DMA) += dma-noop.o
 
 lib-y  += kobject.o klist.o
 obj-y  += lockref.o
diff --git a/lib/dma-noop.c b/lib/dma-noop.c
new file mode 100644
index 000000000000..72145646857e
--- /dev/null
+++ b/lib/dma-noop.c
@@ -0,0 +1,75 @@
+/*
+ *     lib/dma-noop.c
+ *
+ * Simple DMA noop-ops that map 1:1 with memory
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+static void *dma_noop_alloc(struct device *dev, size_t size,
+                           dma_addr_t *dma_handle, gfp_t gfp,
+                           struct dma_attrs *attrs)
+{
+       void *ret;
+
+       ret = (void *)__get_free_pages(gfp, get_order(size));
+       if (ret)
+               *dma_handle = virt_to_phys(ret);
+       return ret;
+}
+
+static void dma_noop_free(struct device *dev, size_t size,
+                         void *cpu_addr, dma_addr_t dma_addr,
+                         struct dma_attrs *attrs)
+{
+       free_pages((unsigned long)cpu_addr, get_order(size));
+}
+
+static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
+                                     unsigned long offset, size_t size,
+                                     enum dma_data_direction dir,
+                                     struct dma_attrs *attrs)
+{
+       return page_to_phys(page) + offset;
+}
+
+static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int 
nents,
+                            enum dma_data_direction dir, struct dma_attrs 
*attrs)
+{
+       int i;
+       struct scatterlist *sg;
+
+       for_each_sg(sgl, sg, nents, i) {
+               void *va;
+
+               BUG_ON(!sg_page(sg));
+               va = sg_virt(sg);
+               sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
+               sg_dma_len(sg) = sg->length;
+       }
+
+       return nents;
+}
+
+static int dma_noop_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+       return 0;
+}
+
+static int dma_noop_supported(struct device *dev, u64 mask)
+{
+       return 1;
+}
+
+struct dma_map_ops dma_noop_ops = {
+       .alloc                  = dma_noop_alloc,
+       .free                   = dma_noop_free,
+       .map_page               = dma_noop_map_page,
+       .map_sg                 = dma_noop_map_sg,
+       .mapping_error          = dma_noop_mapping_error,
+       .dma_supported          = dma_noop_supported,
+};
+
+EXPORT_SYMBOL(dma_noop_ops);
-- 
2.5.0


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