Messages in this thread | | | From | Ohad Ben-Cohen <> | Date | Wed, 7 Sep 2011 09:01:26 +0300 | Subject | Re: [RFC 7/7] iommu/core: split mapping to page sizes as supported by the hardware |
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Hi Cho,
On Wed, Sep 7, 2011 at 4:30 AM, KyongHo Cho <pullip.cho@samsung.com> wrote: > Please find the following link that I submitted for our IOMMU. > https://lkml.org/lkml/2011/7/3/152 > > s5p_iommu_map/unmap accepts any order of physical address and iova > without support of your suggestion if the order is not less than PAGE_SHIFT
That's exactly what I'm trying to prevent; there's no reason to duplicate the exact same logic in every iommu driver.
As a result, your map function is quite big (it even duplicates the same logic for every page size it tries).
Try to rebase your patch on the "iommu/core: split mapping to page sizes as supported by the hardware" patch I've just sent, and see how significantly simpler your code becomes.
Relying on a single implementation, provided by the IOMMU core, means less code to maintain (and debug) and a consistent behavior (across all supported hardware) exposed to users of the IOMMU API.
> But I think IOMMU API must not expect that the caller of iommu_map() knows > about the restriction of IOMMU API implementation.
Right. But I don't think there's any disagreement here ?
If any, then I think that s5p_iommu_map() is more limited than what I propose: if it is given a 64KB region aligned only to a 4KB address, it will BUG_ON() it. While not ideal, I don't think there's any reason not to map it using 4KB pages (which is exactly what the new iommu_map() I propose will do).
Thanks, Ohad.
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