lib/dma-noop.c

   1 /*
   2  *      lib/dma-noop.c
   3  *
   4  * DMA operations that map to physical addresses without flushing memory.
   5  */
   6 #include <linux/export.h>
   7 #include <linux/mm.h>
   8 #include <linux/dma-mapping.h>
   9 #include <linux/scatterlist.h>
  10
  11 static void *dma_noop_alloc(struct device *dev, size_t size,
  12                             dma_addr_t *dma_handle, gfp_t gfp,
  13                             unsigned long attrs)
  14 {
  15         void *ret;
  16
  17         ret = (void *)__get_free_pages(gfp, get_order(size));
  18         if (ret)
  19                 *dma_handle = virt_to_phys(ret);
  20         return ret;
  21 }
  22
  23 static void dma_noop_free(struct device *dev, size_t size,
  24                           void *cpu_addr, dma_addr_t dma_addr,
  25                           unsigned long attrs)
  26 {
  27         free_pages((unsigned long)cpu_addr, get_order(size));
  28 }
  29
  30 static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
  31                                       unsigned long offset, size_t size,
  32                                       enum dma_data_direction dir,
  33                                       unsigned long attrs)
  34 {
  35         return page_to_phys(page) + offset;
  36 }
  37
  38 static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
  39                              enum dma_data_direction dir,
  40                              unsigned long attrs)
  41 {
  42         int i;
  43         struct scatterlist *sg;
  44
  45         for_each_sg(sgl, sg, nents, i) {
  46                 void *va;
  47
  48                 BUG_ON(!sg_page(sg));
  49                 va = sg_virt(sg);
  50                 sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
  51                 sg_dma_len(sg) = sg->length;
  52         }
  53
  54         return nents;
  55 }
  56
  57 static int dma_noop_mapping_error(struct device *dev, dma_addr_t dma_addr)
  58 {
  59         return 0;
  60 }
  61
  62 static int dma_noop_supported(struct device *dev, u64 mask)
  63 {
  64         return 1;
  65 }
  66
  67 const struct dma_map_ops dma_noop_ops = {
  68         .alloc                  = dma_noop_alloc,
  69         .free                   = dma_noop_free,
  70         .map_page               = dma_noop_map_page,
  71         .map_sg                 = dma_noop_map_sg,
  72         .mapping_error          = dma_noop_mapping_error,
  73         .dma_supported          = dma_noop_supported,
  74 };
  75
  76 EXPORT_SYMBOL(dma_noop_ops);