From: Yury Norov <ynorov@nvidia.com>
Date: Mon, 23 Mar 2026 16:17:12 +0000 (-0400)
Subject: lib: count_zeros: unify count_{leading,trailing}_zeros()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=be56db15fcce8bb8bd85f236382276d52ce73d08;p=thirdparty%2Fkernel%2Flinux.git

lib: count_zeros: unify count_{leading,trailing}_zeros()

The 'leading' helper returns BITS_PER_LONG if x == 0, while 'trailing'
one returns COUNT_TRAILING_ZEROS_0, which turns to be -1.

None of the current users explicitly check the returned value for
COUNT_TRAILING_ZEROS_0, except the loongarch, which tests implicitly
for the '>= 0'.

So, align count_trailing_zeros() with the count_leading_zeros(), and
simplify the loongarch handling.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---

diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
index d2acb4d09e73f..3b5268116727c 100644
--- a/arch/loongarch/kvm/intc/eiointc.c
+++ b/arch/loongarch/kvm/intc/eiointc.c
@@ -16,7 +16,7 @@ static void eiointc_set_sw_coreisr(struct loongarch_eiointc *s)
 		ipnum = (s->ipmap >> (irq / 32 * 8)) & 0xff;
 		if (!(s->status & BIT(EIOINTC_ENABLE_INT_ENCODE))) {
 			ipnum = count_trailing_zeros(ipnum);
-			ipnum = (ipnum >= 0 && ipnum < 4) ? ipnum : 0;
+			ipnum = ipnum < 4 ? ipnum : 0;
 		}
 
 		cpuid = ((u8 *)s->coremap)[irq];
@@ -41,7 +41,7 @@ static void eiointc_update_irq(struct loongarch_eiointc *s, int irq, int level)
 	ipnum = (s->ipmap >> (irq / 32 * 8)) & 0xff;
 	if (!(s->status & BIT(EIOINTC_ENABLE_INT_ENCODE))) {
 		ipnum = count_trailing_zeros(ipnum);
-		ipnum = (ipnum >= 0 && ipnum < 4) ? ipnum : 0;
+		ipnum = ipnum < 4 ? ipnum : 0;
 	}
 
 	cpu = s->sw_coremap[irq];
diff --git a/include/linux/count_zeros.h b/include/linux/count_zeros.h
index 5034a30b5c7c7..b72ba3faa036b 100644
--- a/include/linux/count_zeros.h
+++ b/include/linux/count_zeros.h
@@ -10,8 +10,6 @@
 
 #include <asm/bitops.h>
 
-#define COUNT_TRAILING_ZEROS_0 (-1)
-
 /**
  * count_leading_zeros - Count the number of zeros from the MSB back
  * @x: The value
@@ -38,11 +36,11 @@ static inline int count_leading_zeros(unsigned long x)
  *
  * If the LSB of @x is set, the result is 0.
  * If only the MSB of @x is set, then the result is BITS_PER_LONG-1.
- * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0.
+ * If @x is 0 then the result is BITS_PER_LONG.
  */
 static inline int count_trailing_zeros(unsigned long x)
 {
-	return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0;
+	return x ? __ffs(x) : BITS_PER_LONG;
 }
 
 #endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */