Benjamin Herrenschmidt <b...@kernel.crashing.org> writes:
> static inline unsigned long iommu_num_pages(unsigned long addr,
> unsigned long len,
> unsigned long io_page_size)
> {
> unsigned long size = (addr & (io_page_size - 1)) + len;
>
> return DIV_ROUND_UP(size, io_page_size);
> }
>
>
> That doesn't look right to me...
>
> The powerpc iommu code at least uses that with an addr which may not be
> page aligned (ie, result of sg_virt() which include the offset).
>
> The above code will align the start before adding the len which is wrong
addr & (io_page_size - 1) computes the offset into the page pointed to
by addr. Looks right to me.
addr & ~(io_page_size - 1) would round addr down to the start of the
page.
Andreas.
--
Andreas Schwab, sch...@linux-m68k.org
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"And now for something completely different."
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