Commit dbef91ec authored by Martin Wilck's avatar Martin Wilck Committed by Martin K. Petersen
Browse files

scsi: ilog2: create truly constant version for sparse 

Sparse emits errors about ilog2() in array indices because of the use of
__ilog2_32() and __ilog2_64(), rightly so
(https://www.spinics.net/lists/linux-sparse/msg03471.html

).

Create a const_ilog2() variant that works with sparse for this scenario.

(Note: checkpatch.pl complains about missing parentheses, but that
appears to be a false positive. I can get rid of the warning simply by
inserting whitespace, making checkpatch "see" the whole macro).

Signed-off-by: default avatarMartin Wilck <mwilck@suse.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 2217a47d

include/linux/log2.h

+24 −11
Original line number Diff line number Diff line
@@ -72,16 +72,13 @@ unsigned long __rounddown_pow_of_two(unsigned long n) 
}



/**

 * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value

 * const_ilog2 - log base 2 of 32-bit or a 64-bit constant unsigned value

 * @n: parameter

 *

 * constant-capable log of base 2 calculation

 * - this can be used to initialise global variables from constant data, hence

 * the massive ternary operator construction

 *

 * selects the appropriately-sized optimised version depending on sizeof(n)

 * Use this where sparse expects a true constant expression, e.g. for array

 * indices.

 */

#define ilog2(n)				\

#define const_ilog2(n)				\

(						\

	__builtin_constant_p(n) ? (		\

		(n) < 2 ? 0 :			\
@@ -148,6 +145,22 @@ unsigned long __rounddown_pow_of_two(unsigned long n) 
		(n) & (1ULL <<  3) ?  3 :	\

		(n) & (1ULL <<  2) ?  2 :	\

		1) :				\

	-1)



/**

 * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value

 * @n: parameter

 *

 * constant-capable log of base 2 calculation

 * - this can be used to initialise global variables from constant data, hence

 * the massive ternary operator construction

 *

 * selects the appropriately-sized optimised version depending on sizeof(n)

 */

#define ilog2(n) \

( \

	__builtin_constant_p(n) ?	\

	const_ilog2(n) :		\

	(sizeof(n) <= 4) ?		\

	__ilog2_u32(n) :		\

	__ilog2_u64(n)			\

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