dma-mapping: add a dma_mmap_pages helper

Add a helper to map memory allocated using dma_alloc_pages into
a user address space, similar to the dma_alloc_attrs function for
coherent allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Ricardo Ribalda <ribalda@chromium.org>

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index e6d23f117308dfb621c679815ac941d1c8551c6d..157a474ae544162fc681263301dadf1b8bb2da70 100644 (file)
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -563,6 +563,16 @@ Free a region of memory previously allocated using dma_alloc_pages().
 dev, size, dma_handle and dir must all be the same as those passed into
 dma_alloc_pages().  page must be the pointer returned by dma_alloc_pages().
 
+::
+
+       int
+       dma_mmap_pages(struct device *dev, struct vm_area_struct *vma,
+                      size_t size, struct page *page)
+
+Map an allocation returned from dma_alloc_pages() into a user address space.
+dev and size must be the same as those passed into dma_alloc_pages().
+page must be the pointer returned by dma_alloc_pages().
+
 ::
 
        void *

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 2a984cb4d1e037645c8e599223508f1b6d663abe..2b8dce756e1fa1365e32059f3f48aac7d1f015b8 100644 (file)
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -263,6 +263,8 @@ struct page *dma_alloc_pages(struct device *dev, size_t size,
                dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp);
 void dma_free_pages(struct device *dev, size_t size, struct page *page,
                dma_addr_t dma_handle, enum dma_data_direction dir);
+int dma_mmap_pages(struct device *dev, struct vm_area_struct *vma,
+               size_t size, struct page *page);
 
 static inline void *dma_alloc_noncoherent(struct device *dev, size_t size,
                dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index b6a63367993328671fa8ee6faab1d98ae7d852c5..9ce86c77651c6f10819c7f3195a5121844c18bb0 100644 (file)
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -517,6 +517,19 @@ void dma_free_pages(struct device *dev, size_t size, struct page *page,
 }
 EXPORT_SYMBOL_GPL(dma_free_pages);
 
+int dma_mmap_pages(struct device *dev, struct vm_area_struct *vma,
+               size_t size, struct page *page)
+{
+       unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+       if (vma->vm_pgoff >= count || vma_pages(vma) > count - vma->vm_pgoff)
+               return -ENXIO;
+       return remap_pfn_range(vma, vma->vm_start,
+                              page_to_pfn(page) + vma->vm_pgoff,
+                              vma_pages(vma) << PAGE_SHIFT, vma->vm_page_prot);
+}
+EXPORT_SYMBOL_GPL(dma_mmap_pages);
+
 int dma_supported(struct device *dev, u64 mask)
 {
        const struct dma_map_ops *ops = get_dma_ops(dev);