[PATCH v4 09/10] dma-buf-map: Add memcpy and pointer-increment interfaces

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

To do framebuffer updates, one needs memcpy from system memory and a
pointer-increment function. Add both interfaces with documentation.

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
 include/linux/dma-buf-map.h | 72 +++++++++++++++++++++++++++++++------
 1 file changed, 62 insertions(+), 10 deletions(-)

diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h
index 2e8bbecb5091..6ca0f304dda2 100644
--- a/include/linux/dma-buf-map.h
+++ b/include/linux/dma-buf-map.h
@@ -32,6 +32,14 @@
  * accessing the buffer. Use the returned instance and the helper functions
  * to access the buffer's memory in the correct way.
  *
+ * The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are
+ * actually independent from the dma-buf infrastructure. When sharing buffers
+ * among devices, drivers have to know the location of the memory to access
+ * the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>`
+ * solves this problem for dma-buf and its users. If other drivers or
+ * sub-systems require similar functionality, the type could be generalized
+ * and moved to a more prominent header file.
+ *
  * Open-coding access to :c:type:`struct dma_buf_map <dma_buf_map>` is
  * considered bad style. Rather then accessing its fields directly, use one
  * of the provided helper functions, or implement your own. For example,
@@ -51,6 +59,14 @@
  *
  *     dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf);
  *
+ * Instances of struct dma_buf_map do not have to be cleaned up, but
+ * can be cleared to NULL with dma_buf_map_clear(). Cleared mappings
+ * always refer to system memory.
+ *
+ * .. code-block:: c
+ *
+ *     dma_buf_map_clear(&map);
+ *
  * Test if a mapping is valid with either dma_buf_map_is_set() or
  * dma_buf_map_is_null().
  *
@@ -73,17 +89,19 @@
  *     if (dma_buf_map_is_equal(&sys_map, &io_map))
  *             // always false
  *
- * Instances of struct dma_buf_map do not have to be cleaned up, but
- * can be cleared to NULL with dma_buf_map_clear(). Cleared mappings
- * always refer to system memory.
+ * A set up instance of struct dma_buf_map can be used to access or manipulate
+ * the buffer memory. Depending on the location of the memory, the provided
+ * helpers will pick the correct operations. Data can be copied into the memory
+ * with dma_buf_map_memcpy_to(). The address can be manipulated with
+ * dma_buf_map_incr().
  *
- * The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are
- * actually independent from the dma-buf infrastructure. When sharing buffers
- * among devices, drivers have to know the location of the memory to access
- * the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>`
- * solves this problem for dma-buf and its users. If other drivers or
- * sub-systems require similar functionality, the type could be generalized
- * and moved to a more prominent header file.
+ * .. code-block:: c
+ *
+ *     const void *src = ...; // source buffer
+ *     size_t len = ...; // length of src
+ *
+ *     dma_buf_map_memcpy_to(&map, src, len);
+ *     dma_buf_map_incr(&map, len); // go to first byte after the memcpy
  */
 
 /**
@@ -210,4 +228,38 @@ static inline void dma_buf_map_clear(struct dma_buf_map 
*map)
        }
 }
 
+/**
+ * dma_buf_map_memcpy_to - Memcpy into dma-buf mapping
+ * @dst:       The dma-buf mapping structure
+ * @src:       The source buffer
+ * @len:       The number of byte in src
+ *
+ * Copies data into a dma-buf mapping. The source buffer is in system
+ * memory. Depending on the buffer's location, the helper picks the correct
+ * method of accessing the memory.
+ */
+static inline void dma_buf_map_memcpy_to(struct dma_buf_map *dst, const void 
*src, size_t len)
+{
+       if (dst->is_iomem)
+               memcpy_toio(dst->vaddr_iomem, src, len);
+       else
+               memcpy(dst->vaddr, src, len);
+}
+
+/**
+ * dma_buf_map_incr - Increments the address stored in a dma-buf mapping
+ * @map:       The dma-buf mapping structure
+ * @incr:      The number of bytes to increment
+ *
+ * Increments the address stored in a dma-buf mapping. Depending on the
+ * buffer's location, the correct value will be updated.
+ */
+static inline void dma_buf_map_incr(struct dma_buf_map *map, size_t incr)
+{
+       if (map->is_iomem)
+               map->vaddr_iomem += incr;
+       else
+               map->vaddr += incr;
+}
+
 #endif /* __DMA_BUF_MAP_H__ */
-- 
2.28.0