Re: [PATCH 2/5] dma-direct: add an explicit dma_direct_get_required_mask
From: Christoph Hellwig <hch@lst.de>
Date: 2018-09-27 15:28:22
Also in:
linux-iommu, lkml
On Thu, Sep 27, 2018 at 03:12:25PM +0100, Robin Murphy wrote:
quoted
+u64 dma_direct_get_required_mask(struct device *dev) +{ + u64 max_dma = phys_to_dma_direct(dev, (max_pfn - 1) << PAGE_SHIFT); + + return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;I think that may as well just use __fls64() - it seems reasonable to assume max_dma > 0. Otherwise,
Is there any good reason to micro-optimize given that this isn't a fast path?