Hi Thomas.
On Thu, Oct 15, 2020 at 02:38:05PM +0200, Thomas Zimmermann wrote:
> 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>
Looks good.
Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> ---
> 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
