kernel/dma/virt.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * DMA operations that map to virtual addresses without flushing memory.
   4  */
   5 #include <linux/export.h>
   6 #include <linux/mm.h>
   7 #include <linux/dma-mapping.h>
   8 #include <linux/scatterlist.h>
   9
  10 static void *dma_virt_alloc(struct device *dev, size_t size,
  11                             dma_addr_t *dma_handle, gfp_t gfp,
  12                             unsigned long attrs)
  13 {
  14         void *ret;
  15
  16         ret = (void *)__get_free_pages(gfp | __GFP_ZERO, get_order(size));
  17         if (ret)
  18                 *dma_handle = (uintptr_t)ret;
  19         return ret;
  20 }
  21
  22 static void dma_virt_free(struct device *dev, size_t size,
  23                           void *cpu_addr, dma_addr_t dma_addr,
  24                           unsigned long attrs)
  25 {
  26         free_pages((unsigned long)cpu_addr, get_order(size));
  27 }
  28
  29 static dma_addr_t dma_virt_map_page(struct device *dev, struct page *page,
  30                                     unsigned long offset, size_t size,
  31                                     enum dma_data_direction dir,
  32                                     unsigned long attrs)
  33 {
  34         return (uintptr_t)(page_address(page) + offset);
  35 }
  36
  37 static int dma_virt_map_sg(struct device *dev, struct scatterlist *sgl,
  38                            int nents, enum dma_data_direction dir,
  39                            unsigned long attrs)
  40 {
  41         int i;
  42         struct scatterlist *sg;
  43
  44         for_each_sg(sgl, sg, nents, i) {
  45                 BUG_ON(!sg_page(sg));
  46                 sg_dma_address(sg) = (uintptr_t)sg_virt(sg);
  47                 sg_dma_len(sg) = sg->length;
  48         }
  49
  50         return nents;
  51 }
  52
  53 const struct dma_map_ops dma_virt_ops = {
  54         .alloc                  = dma_virt_alloc,
  55         .free                   = dma_virt_free,
  56         .map_page               = dma_virt_map_page,
  57         .map_sg                 = dma_virt_map_sg,
  58 };
  59 EXPORT_SYMBOL(dma_virt_ops);