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author | venkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com> | 2008-12-18 22:41:33 +0300 |
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committer | H. Peter Anvin <hpa@zytor.com> | 2008-12-19 00:30:16 +0300 |
commit | a2ced6e173e0c93870f79856e97825f4e180891e (patch) | |
tree | c0bc36dcc594197f392f82f2cca36167ff9584e4 /Documentation/x86 | |
parent | 2520bd3123c00272f818a176c92d03c7d0a113d6 (diff) | |
download | linux-a2ced6e173e0c93870f79856e97825f4e180891e.tar.xz |
x86: PAT: update documentation to cover pgprot and remap_pfn related changes - v3
Impact: Documentation only.
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>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/x86')
-rw-r--r-- | Documentation/x86/pat.txt | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt index c93ff5f4c0dd..1784ff276997 100644 --- a/Documentation/x86/pat.txt +++ b/Documentation/x86/pat.txt @@ -80,6 +80,30 @@ pci proc | -- | -- | WC | | | | | ------------------------------------------------------------------- +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 |