[PATCH v5 next 1/9] lib: mul_u64_u64_div_u64() rename parameter 'c' to 'd'

David Laight
2025-11-05T20:10:53Z

Change to prototype from mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
to mul_u64_u64_div_u64(u64 a, u64 b, u64 d).
Using 'd' for 'divisor' makes more sense.

An upcoming change adds a 'c' parameter to calculate (a * b + c)/d.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
Reviewed-by: Nicolas Pitre <npitre@baylibre.com>
---
lib/math/div64.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/math/div64.c b/lib/math/div64.c
index bf77b9843175..0ebff850fd4d 100644
--- a/lib/math/div64.c
+++ b/lib/math/div64.c
@@ -184,10 +184,10 @@ u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
EXPORT_SYMBOL(iter_div_u64_rem);

#ifndef mul_u64_u64_div_u64
-u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
+u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 d)
{
if (ilog2(a) + ilog2(b) <= 62)
- return div64_u64(a * b, c);
+ return div64_u64(a * b, d);

#if defined(__SIZEOF_INT128__)

@@ -212,37 +212,37 @@ u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)

#endif

- /* make sure c is not zero, trigger runtime exception otherwise */
- if (unlikely(c == 0)) {
+ /* make sure d is not zero, trigger runtime exception otherwise */
+ if (unlikely(d == 0)) {
unsigned long zero = 0;

OPTIMIZER_HIDE_VAR(zero);
return ~0UL/zero;
}

- int shift = __builtin_ctzll(c);
+ int shift = __builtin_ctzll(d);

/* try reducing the fraction in case the dividend becomes <= 64 bits */
if ((n_hi >> shift) == 0) {
u64 n = shift ? (n_lo >> shift) | (n_hi << (64 - shift)) : n_lo;

- return div64_u64(n, c >> shift);
+ return div64_u64(n, d >> shift);
/*
* The remainder value if needed would be:
- * res = div64_u64_rem(n, c >> shift, &rem);
+ * res = div64_u64_rem(n, d >> shift, &rem);
* rem = (rem << shift) + (n_lo - (n << shift));
*/
}

- if (n_hi >= c) {
+ if (n_hi >= d) {
/* overflow: result is unrepresentable in a u64 */
return -1;
}

/* Do the full 128 by 64 bits division */

- shift = __builtin_clzll(c);
- c <<= shift;
+ shift = __builtin_clzll(d);
+ d <<= shift;

int p = 64 + shift;
u64 res = 0;
@@ -257,8 +257,8 @@ u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
n_hi <<= shift;
n_hi |= n_lo >> (64 - shift);
n_lo <<= shift;
- if (carry || (n_hi >= c)) {
- n_hi -= c;
+ if (carry || (n_hi >= d)) {
+ n_hi -= d;
res |= 1ULL << p;
}
} while (n_hi);
--
2.39.5