diff options
| author | Martin Wilck | 2018-04-18 01:35:06 +0200 |
|---|---|---|
| committer | Martin K. Petersen | 2018-04-20 21:57:32 +0200 |
| commit | dbef91ec5482239055dd2db8ec656fc13d382add (patch) | |
| tree | 713484f124faf033bd7970cfbb8cdcfd080891b2 /include/linux/log2.h | |
| parent | scsi: storvsc: Select channel based on available percentage of ring buffer to... (diff) | |
| download | kernel-qcow2-linux-dbef91ec5482239055dd2db8ec656fc13d382add.tar.gz kernel-qcow2-linux-dbef91ec5482239055dd2db8ec656fc13d382add.tar.xz kernel-qcow2-linux-dbef91ec5482239055dd2db8ec656fc13d382add.zip | |
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>
Diffstat (limited to 'include/linux/log2.h')
| -rw-r--r-- | include/linux/log2.h | 35 |
1 files changed, 24 insertions, 11 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h index 41a1ae010993..2af7f77866d0 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -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) \ ) /** |