[PATCH] avoid signed vs unsigned comparison in efi_range_is_wc()

[Jesper Juhl]

This little function in include/linux/efi.h :

static inline int efi_range_is_wc(unsigned long start, unsigned long len)
{
        int i;

        for (i = 0; i < len; i += (1UL << EFI_PAGE_SHIFT)) {
                unsigned long paddr = __pa(start + i);
                if (!(efi_mem_attributes(paddr) & EFI_MEMORY_WC))
                        return 0;
        }
        /* The range checked out */
        return 1;
}

generates this warning when building with gcc -W : 

include/linux/efi.h: In function `efi_range_is_wc':
include/linux/efi.h:320: warning: comparison between signed and unsigned

It looks to me like a significantly large 'len' passed in could cause the 
loop to never end. Isn't it safer to make 'i' an unsigned long as well? 
Like this little patch below (which of course also kills the warning) :


Signed-off-by: Jesper Juhl <juhl-lkml@xxxxxx>

diff -up linux-2.6.11-mm4-orig/include/linux/efi.h linux-2.6.11-mm4/include/linux/efi.h
--- linux-2.6.11-mm4-orig/include/linux/efi.h	2005-03-16 15:45:35.000000000 +0100
+++ linux-2.6.11-mm4/include/linux/efi.h	2005-03-18 00:34:36.000000000 +0100
@@ -315,7 +315,7 @@ extern struct efi_memory_map memmap;
  */
 static inline int efi_range_is_wc(unsigned long start, unsigned long len)
 {
-	int i;
+	unsigned long i;
 
 	for (i = 0; i < len; i += (1UL << EFI_PAGE_SHIFT)) {
 		unsigned long paddr = __pa(start + i);



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