Hi,
This is second attempt to bring some safeness to dma_attrs. In v1 [0] I added const to data pointed by attrs. However Christoph Hellwig suggested getting rid of struct dma_attrs in favor of some simpler data type.
Benefits of unsigned long for dma_attrs: 1. This is just simpler. Both in terms of reading the code and setting attributes. Instead of initializing local attributes on the stack and passing pointer to it to dma_set_attr(), just set the bits.
2. It brings safeness and checking for const correctness because the attributes are passed by value.
The problem is that the patch touches the dma-mapping API so all the users have to be converted (ARM and ARM64 as of now).
Any ideas to split it per smaller patches?
The work is not finished yet, I would rather get some feedback before progressing further.
Best regards, Krzysztof
Krzysztof Kozlowski (1): dma-mapping: Use unsigned long for dma_attrs
Documentation/DMA-API.txt | 2 +- Documentation/DMA-attributes.txt | 2 +- arch/arm/include/asm/dma-mapping.h | 13 ++-- arch/arm/include/asm/xen/page-coherent.h | 16 ++--- arch/arm/mm/dma-mapping.c | 82 +++++++++++------------ arch/arm/xen/mm.c | 4 +- arch/arm64/mm/dma-mapping.c | 57 ++++++++-------- drivers/gpu/drm/exynos/exynos_drm_fbdev.c | 2 +- drivers/gpu/drm/exynos/exynos_drm_g2d.c | 1 - drivers/gpu/drm/exynos/exynos_drm_gem.c | 20 +++--- drivers/gpu/drm/exynos/exynos_drm_gem.h | 2 +- drivers/iommu/dma-iommu.c | 6 +- drivers/xen/swiotlb-xen.c | 14 ++-- include/linux/dma-attrs.h | 71 -------------------- include/linux/dma-iommu.h | 6 +- include/linux/dma-mapping.h | 105 +++++++++++++++++------------- include/linux/swiotlb.h | 10 +-- include/xen/swiotlb-xen.h | 12 ++-- lib/dma-noop.c | 9 +-- lib/swiotlb.c | 13 ++-- 20 files changed, 195 insertions(+), 252 deletions(-) delete mode 100644 include/linux/dma-attrs.h