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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: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Martin Wilck 2018-04-18 01:35:06 +02:00 committed by Martin K. Petersen
parent 2217a47de4
commit dbef91ec54
1 changed files with 24 additions and 11 deletions
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35
include/linux/log2.h
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@ -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 : \
@ -147,10 +144,26 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
(n) & (1ULL << 4) ? 4 : \
(n) & (1ULL << 3) ? 3 : \
(n) & (1ULL << 2) ? 2 : \
1 ) : \
(sizeof(n) <= 4) ? \
__ilog2_u32(n) : \
__ilog2_u64(n) \
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) \
)
/**