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Subject[PATCH] Minor fixes to generic do_div

While tracking down a problem recently, I noticed the description of
do_div() is not quite right. We also don't check that 'n' is 64-bit
when running on a 64-bit machine (this would have caused warnings to
appear on more configurations if we had). And finally, the indentation
of the \ characters in the 64-bit case don't match those in the 32-bit case,
so change those to match.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>

diff --git a/include/asm-generic/div64.h b/include/asm-generic/div64.h
index 8f4e319..0edfb96 100644
--- a/include/asm-generic/div64.h
+++ b/include/asm-generic/div64.h
@@ -6,10 +6,10 @@ #define _ASM_GENERIC_DIV64_H
*
* The semantics of do_div() are:
*
- * uint32_t do_div(uint64_t *n, uint32_t base)
+ * uint32_t do_div(uint64_t n, uint32_t base)
* {
- * uint32_t remainder = *n % base;
- * *n = *n / base;
+ * uint32_t remainder = n % base;
+ * n = n / base;
* return remainder;
* }
*
@@ -22,12 +22,16 @@ #include <linux/compiler.h>

#if BITS_PER_LONG == 64

-# define do_div(n,base) ({ \
- uint32_t __base = (base); \
- uint32_t __rem; \
- __rem = ((uint64_t)(n)) % __base; \
- (n) = ((uint64_t)(n)) / __base; \
- __rem; \
+/* The unnecessary pointer compare is there
+ * to check for type safety (n must be 64bit)
+ */
+# define do_div(n,base) ({ \
+ uint32_t __base = (base); \
+ uint32_t __rem; \
+ (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
+ __rem = ((uint64_t)(n)) % __base; \
+ (n) = ((uint64_t)(n)) / __base; \
+ __rem; \
})

#elif BITS_PER_LONG == 32
-
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