On 29/05/2019 09:15, Nathan Chancellor wrote:
Clang warns:drivers/iommu/dma-iommu.c:897:6: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses] if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0) ^ ~~ drivers/iommu/dma-iommu.c:897:6: note: add parentheses after the '!' to evaluate the comparison first if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0) ^ ( ) drivers/iommu/dma-iommu.c:897:6: note: add parentheses around left hand side expression to silence this warning if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0) ^ ( ) 1 warning generated. Judging from the rest of the commit and the conditional in iommu_dma_map_sg, either if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) or if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0) was intended, not a combination of the two. I personally think that the former is easier to understand so use that.
Good catch, thanks Nathan. Looks like this was an unintentional mangling while ratifying the couple of odd "x == 0" instances to "!x" in the move. The effective double-negation is not what we want at all.
Reviewed-by: Robin Murphy <[email protected]>
Fixes: 06d60728ff5c ("iommu/dma: move the arm64 wrappers to common code") Link: https://github.com/ClangBuiltLinux/linux/issues/497 Signed-off-by: Nathan Chancellor <[email protected]> --- drivers/iommu/dma-iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 0cd49c2d3770..0dee374fc64a 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -894,7 +894,7 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, struct scatterlist *tmp; int i;- if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)+ if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir);/*
