[patch 5/5] x86 PAT: pfnmap documentation update changes

venkatesh.pallipadi
2008-12-19T21:51:35Z

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Documentation updates as per Randy Dunlap's comments.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>

---
Documentation/x86/pat.txt | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

Index: linux-2.6/Documentation/x86/pat.txt
===================================================================
--- linux-2.6.orig/Documentation/x86/pat.txt 2008-12-19 09:55:04.000000000 -0800
+++ linux-2.6/Documentation/x86/pat.txt 2008-12-19 10:15:46.000000000 -0800
@@ -82,23 +82,23 @@ pci proc | -- | -

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

-Drivers wanting to export some pages to userspace, do it by using mmap
+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
+With PAT support, a new API pgprot_writecombine is being added. So, drivers 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()
+Note that this set of APIs only works with IO (non RAM) regions. If driver
+wants to export a 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.

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