Hello, On 6/20/2013 7:49 AM, Hiroshi Doyu wrote:
In Tegra SoC, IOMMU can set some mapping attribute for each page, for exmaple, READable, and WRITEable. We'd like to use this feature *newly* for robustness, where read-only pages can be protected from being overwritten by wrong operation. We have been using IOMMU via DMA mapping API(ARM). DMA mapping API currently doesn't use "prot" parameter when calling IOMMU API. So this series tries to pass "struct dma_attrs *attrs" via "int prot" in IOMMU API. I'm not so sure if this implementation is right or not because: - Casting (struct dma_attrs *) to (int) in DMA API doesn't look nice. - IOMMU layer needs to cast (int) back to (struct dma_attrs *) again, which can be considered as violation of layers. If you have any implementations/suggestions, it would be really helpful. This series isn't applied cleanly but this is posted to request for comments.
Using DMA attributes for this seems to be a bad idea. The dma direction parameter is much more appropriate. Will Deacon recently posted a patch which does it right, see: https://git.linaro.org/gitweb?p=people/mszyprowski/linux-dma-mapping.git;a=commit;h=8fc3749bd31d139db58f874e093255fe62505968
Hiroshi Doyu (3): common: DMA-mapping: add DMA_ATTR_READ_ONLY attribute ARM: dma-mapping: Pass DMA attrs as IOMMU prot iommu/tegra: smmu: Support read-only mapping arch/arm/mm/dma-mapping.c | 34 +++++++++++++++++++++------------- drivers/iommu/tegra-smmu.c | 41 +++++++++++++++++++++++++++++------------ include/linux/dma-attrs.h | 1 + 3 files changed, 51 insertions(+), 25 deletions(-)
Best regards -- Marek Szyprowski Samsung R&D Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
