lib/dma-virt.c

   1 /*
   2  *      lib/dma-virt.c
   3  *
   4  * DMA operations that map to virtual 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_virt_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 = (uintptr_t)ret;
  20         return ret;
  21 }
  22
  23 static void dma_virt_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_virt_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 (uintptr_t)(page_address(page) + offset);
  36 }
  37
  38 static int dma_virt_map_sg(struct device *dev, struct scatterlist *sgl,
  39                            int nents, 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                 BUG_ON(!sg_page(sg));
  47                 sg_dma_address(sg) = (uintptr_t)sg_virt(sg);
  48                 sg_dma_len(sg) = sg->length;
  49         }
  50
  51         return nents;
  52 }
  53
  54 static int dma_virt_mapping_error(struct device *dev, dma_addr_t dma_addr)
  55 {
  56         return false;
  57 }
  58
  59 static int dma_virt_supported(struct device *dev, u64 mask)
  60 {
  61         return true;
  62 }
  63
  64 const struct dma_map_ops dma_virt_ops = {
  65         .alloc                  = dma_virt_alloc,
  66         .free                   = dma_virt_free,
  67         .map_page               = dma_virt_map_page,
  68         .map_sg                 = dma_virt_map_sg,
  69         .mapping_error          = dma_virt_mapping_error,
  70         .dma_supported          = dma_virt_supported,
  71 };
  72 EXPORT_SYMBOL(dma_virt_ops);