Commit a8463d4b authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Michael S. Tsirkin

dma: Provide simple noop dma ops

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: default avatarChristian Borntraeger <>
Reviewed-by: default avatarJoerg Roedel <>
Signed-off-by: default avatarAndy Lutomirski <>
Signed-off-by: default avatarMichael S. Tsirkin <>
parent e1f33be9
......@@ -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
......@@ -18,6 +18,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.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
* 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;
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,
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