[PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation

From: Russell King (Oracle)
Date: Fri Oct 28 2022 - 12:48:04 EST


Document the ARMv5 bit offset calculation code.

Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
---
arch/arm/lib/findbit.S | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 7fd3600db8ef..4c584bc4704b 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -172,10 +172,10 @@ ENDPROC(_find_next_bit_be)
.L_found:
#if __LINUX_ARM_ARCH__ >= 5
rsb r0, r3, #0
- and r3, r3, r0
- clz r3, r3
- rsb r3, r3, #31
- add r0, r2, r3
+ and r3, r3, r0 @ mask out lowest bit set
+ clz r3, r3 @ count high zero bits
+ rsb r3, r3, #31 @ offset of first set bit
+ add r0, r2, r3 @ add offset of first set bit
#else
tst r3, #0x0f
addeq r2, r2, #4
--
2.30.2