Messages in this thread Patch in this message | | | Date | Wed, 12 Nov 2008 13:26:55 -0800 | From | Venkatesh Pallipadi <> | Subject | [patch 8/8] x86 PAT: update documentation to cover pgprot and remap_pfn related changes |
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Add documentation related to pgprot_* change.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> --- Documentation/x86/pat.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
Index: tip/Documentation/x86/pat.txt =================================================================== --- tip.orig/Documentation/x86/pat.txt 2008-11-06 09:44:10.000000000 -0800 +++ tip/Documentation/x86/pat.txt 2008-11-06 16:19:05.000000000 -0800 @@ -80,6 +80,30 @@ pci proc | -- | - | | | | ------------------------------------------------------------------- +Advanced APIs for drivers +------------------------- +A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range, +vm_insert_pfn + +Drivers wanting to export some pages to userspace, do it by using mmap +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 +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 +wants to export RAM region, it has to do set_memory_uc() or set_memory_wc() +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. + + + Notes: -- in the above table mean "Not suggested usage for the API". Some of the --'s --
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