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    SubjectRe: [patch 7/7] x86 PAT: update documentation to cover pgprot and remap_pfn related changes - v3
    venkatesh.pallipadi@intel.com wrote:

    +Advanced APIs for drivers
    +-------------------------
    +A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range,

    to users
    or to userspace

    +vm_insert_pfn
    +
    +Drivers wanting to export some pages to userspace, do it by using mmap

    Drop comma.

    +interface and a combination of
    +1) pgprot_noncached()
    +2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn()
    +
    +With pat support, a new API pgprot_writecombine is being added. So, driver can

    s/pat/PAT/
    s/driver/drivers/ or s/driver/a driver/

    +continue to use the above sequence, with either pgprot_noncached() or
    +pgprot_writecombine() in step 1, followed by step 2.
    +
    +In addition, step 2 internally tracks the region as UC or WC in memtype
    +list in order to ensure no conflicting mapping.
    +
    +Note that this set of APIs only work with IO (non RAM) regions. If driver

    works with IO (non-RAM) regions. If a driver

    +wants to export RAM region, it has to do set_memory_uc() or set_memory_wc()

    export a RAM region,

    +as step 0 above and also track the usage of those pages and use set_memory_wb()
    +before the page is freed to free pool.


    --
    ~Randy


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