Am 26.01.22 um 21:36 schrieb Lucas De Marchi:
When dma_buf_map struct is passed around, it's useful to be able to initialize a second map that takes care of reading/writing to an offset of the original map. Add a helper that copies the struct and add the offset to the proper address. Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx> Cc: Christian König <christian.koenig@xxxxxxx> Cc: linux-media@xxxxxxxxxxxxxxx Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> --- include/linux/dma-buf-map.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h index 65e927d9ce33..3514a859f628 100644 --- a/include/linux/dma-buf-map.h +++ b/include/linux/dma-buf-map.h @@ -131,6 +131,35 @@ struct dma_buf_map { .is_iomem = false, \ }+/**+ * DMA_BUF_MAP_INIT_OFFSET - Initializes struct dma_buf_map from another dma_buf_map + * @map_: The dma-buf mapping structure to copy from + * @offset: Offset to add to the other mapping + * + * Initializes a new dma_buf_struct based on another. This is the equivalent of doing: + * + * .. code-block: c + * + * dma_buf_map map = other_map; + * dma_buf_map_incr(&map, &offset); + * + * Example usage: + * + * .. code-block: c + * + * void foo(struct device *dev, struct dma_buf_map *base_map) + * { + * ... + * struct dma_buf_map = DMA_BUF_MAP_INIT_OFFSET(base_map, FIELD_OFFSET); + * ... + * } + */ +#define DMA_BUF_MAP_INIT_OFFSET(map_, offset_) (struct dma_buf_map) \ + { \ + .vaddr = (map_)->vaddr + (offset_), \ + .is_iomem = (map_)->is_iomem, \ + } +
It's illegal to access .vaddr with raw pointer. Always use a dma_buf_memcpy_() interface. So why would you need this macro when you have dma_buf_memcpy_*() with an offset parameter?
I've also been very careful to distinguish between .vaddr and .vaddr_iomem, even in places where I wouldn't have to. This macro breaks the assumption.
Best regards Thomas
/** * dma_buf_map_set_vaddr - Sets a dma-buf mapping structure to an address in system memory * @map: The dma-buf mapping structure
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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