[patch 2/6] x86 PAT: consolidate old memtype new memtype check into a function

[venkatesh . pallipadi]

Move the new memtype old memtype allowed check to header so that is can be
shared by other users. Subsequent patch uses this in pat.c in remap_pfn_range()
code path. No functionality change in this patch.

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

---
 arch/x86/include/asm/pgtable.h |   19 +++++++++++++++++++
 arch/x86/pci/i386.c            |   12 +-----------
 2 files changed, 20 insertions(+), 11 deletions(-)

Index: linux-2.6/arch/x86/include/asm/pgtable.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/pgtable.h	2009-01-07 15:00:34.000000000 -0800
+++ linux-2.6/arch/x86/include/asm/pgtable.h	2009-01-07 16:03:25.000000000 -0800
@@ -341,6 +341,25 @@ static inline pgprot_t pgprot_modify(pgp
 
 #define canon_pgprot(p) __pgprot(pgprot_val(p) & __supported_pte_mask)
 
+static inline int is_new_memtype_allowed(unsigned long flags,
+						unsigned long new_flags)
+{
+	/*
+	 * Certain new memtypes are not allowed with certain
+	 * requested memtype:
+	 * - request is uncached, return cannot be write-back
+	 * - request is write-combine, return cannot be write-back
+	 */
+	if ((flags == _PAGE_CACHE_UC_MINUS &&
+	     new_flags == _PAGE_CACHE_WB) ||
+	    (flags == _PAGE_CACHE_WC &&
+	     new_flags == _PAGE_CACHE_WB)) {
+		return 0;
+	}
+
+	return 1;
+}
+
 #ifndef __ASSEMBLY__
 /* Indicate that x86 has its own track and untrack pfn vma functions */
 #define __HAVE_PFNMAP_TRACKING
Index: linux-2.6/arch/x86/pci/i386.c
===================================================================
--- linux-2.6.orig/arch/x86/pci/i386.c	2009-01-07 15:00:34.000000000 -0800
+++ linux-2.6/arch/x86/pci/i386.c	2009-01-07 16:03:20.000000000 -0800
@@ -314,17 +314,7 @@ int pci_mmap_page_range(struct pci_dev *
 		return retval;
 
 	if (flags != new_flags) {
-		/*
-		 * Do not fallback to certain memory types with certain
-		 * requested type:
-		 * - request is uncached, return cannot be write-back
-		 * - request is uncached, return cannot be write-combine
-		 * - request is write-combine, return cannot be write-back
-		 */
-		if ((flags == _PAGE_CACHE_UC_MINUS &&
-		     (new_flags == _PAGE_CACHE_WB)) ||
-		    (flags == _PAGE_CACHE_WC &&
-		     new_flags == _PAGE_CACHE_WB)) {
+		if (!is_new_memtype_allowed(flags, new_flags)) {
 			free_memtype(addr, addr+len);
 			return -EINVAL;
 		}

-- 

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