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lib: crypto: fix comments for count_leading_zeros()

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count_leading_zeros() is based on fls(), which is defined for x == 0,
contrary to __ffs() family. The comment in crypto/mpi erroneously
states that the function may return undef in such case.

Fix the comment together with the outdated function signature, and now
that COUNT_LEADING_ZEROS_0 is not referenced in the codebase, get rid of
it too.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
This commit is contained in:
Yury Norov
2026-03-10 16:53:02 -04:00
parent c6a98dff41
commit 18c4889965
2 changed files with 5 additions and 7 deletions
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4
include/linux/count_zeros.h
View File

@@ -18,7 +18,7 @@
*
* If the MSB of @x is set, the result is 0.
* If only the LSB of @x is set, then the result is BITS_PER_LONG-1.
* If @x is 0 then the result is COUNT_LEADING_ZEROS_0.
* If @x is 0 then the result is BITS_PER_LONG.
*/
static inline int count_leading_zeros(unsigned long x)
{
@@ -28,8 +28,6 @@ static inline int count_leading_zeros(unsigned long x)
return BITS_PER_LONG - fls64(x);
}
#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG
/**
* count_trailing_zeros - Count the number of zeros from the LSB forwards
* @x: The value

8
lib/crypto/mpi/longlong.h
View File

@@ -66,12 +66,12 @@
* denominator). Like udiv_qrnnd but the numbers are signed. The quotient
* is rounded towards 0.
*
* 5) count_leading_zeros(count, x) counts the number of zero-bits from the
* 5) count_leading_zeros(x) counts the number of zero-bits from the
* msb to the first non-zero bit in the UWtype X. This is the number of
* steps X needs to be shifted left to set the msb. Undefined for X == 0,
* unless the symbol COUNT_LEADING_ZEROS_0 is defined to some value.
* steps X needs to be shifted left to set the msb.
* count_leading_zeros(0) == BITS_PER_LONG
*
* 6) count_trailing_zeros(count, x) like count_leading_zeros, but counts
* 6) count_trailing_zeros() like count_leading_zeros(), but counts
* from the least significant end.
*
* 7) add_ssaaaa(high_sum, low_sum, high_addend_1, low_addend_1,