The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     9c94c14ca39577b6324c667d8450ffa19fc1e5c4
Gitweb:        https://git.kernel.org/tip/9c94c14ca39577b6324c667d8450ffa19fc1e5c4
Author:        Kuan-Wei Chiu <visitorckw@gmail.com>
AuthorDate:    Thu, 27 Feb 2025 13:55:45 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 27 Feb 2025 14:00:30 +01:00

x86/bootflag: Replace open-coded parity calculation with parity8()

Refactor parity calculations to use the standard parity8() helper. This
change eliminates redundant implementations and improves code
efficiency.

[ ubizjak: Updated the patch to apply to the latest x86 tree. ]

Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250227125616.2253774-1-ubizjak@gmail.com
---
 arch/x86/kernel/bootflag.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c
index b935c3e..73274d7 100644
--- a/arch/x86/kernel/bootflag.c
+++ b/arch/x86/kernel/bootflag.c
@@ -8,6 +8,7 @@
 #include <linux/string.h>
 #include <linux/spinlock.h>
 #include <linux/acpi.h>
+#include <linux/bitops.h>
 #include <asm/io.h>
 
 #include <linux/mc146818rtc.h>
@@ -20,25 +21,12 @@
 
 int sbf_port __initdata = -1;	/* set via acpi_boot_init() */
 
-static bool __init parity(u8 v)
-{
-	int x = 0;
-	int i;
-
-	for (i = 0; i < 8; i++) {
-		x ^= (v & 1);
-		v >>= 1;
-	}
-
-	return !!x;
-}
-
 static void __init sbf_write(u8 v)
 {
 	unsigned long flags;
 
 	if (sbf_port != -1) {
-		if (!parity(v))
+		if (!parity8(v))
 			v ^= SBF_PARITY;
 
 		printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n",
@@ -69,7 +57,7 @@ static bool __init sbf_value_valid(u8 v)
 {
 	if (v & SBF_RESERVED)		/* Reserved bits */
 		return false;
-	if (!parity(v))
+	if (!parity8(v))
 		return false;
 
 	return true;

Hi Ingo,

On Thu, Feb 27, 2025 at 01:15:13PM -0000, tip-bot2 for Kuan-Wei Chiu wrote:
> The following commit has been merged into the x86/boot branch of tip:
> 
> Commit-ID:     9c94c14ca39577b6324c667d8450ffa19fc1e5c4
> Gitweb:        https://git.kernel.org/tip/9c94c14ca39577b6324c667d8450ffa19fc1e5c4
> Author:        Kuan-Wei Chiu <visitorckw@gmail.com>
> AuthorDate:    Thu, 27 Feb 2025 13:55:45 +01:00
> Committer:     Ingo Molnar <mingo@kernel.org>
> CommitterDate: Thu, 27 Feb 2025 14:00:30 +01:00
> 
> x86/bootflag: Replace open-coded parity calculation with parity8()
> 
> Refactor parity calculations to use the standard parity8() helper. This
> change eliminates redundant implementations and improves code
> efficiency.
> 
> [ ubizjak: Updated the patch to apply to the latest x86 tree. ]
> 
> Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com>
> Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Link: https://lore.kernel.org/r/20250227125616.2253774-1-ubizjak@gmail.com

Thanks for accepting this patch.

Based on the previous email discussion, I plan to rename parity8() to
parity_odd() in the next version of the parity patch series (though I'm
not too confident it will be accepted...). If I base the series on the
current linux-next tree, it might cause conflicts when other
maintainers apply it to their own trees. On the other hand, if I base
it on Linus's tree, it would conflict with the x86 tree.

I'm not sure which tree I should base the next version on. Since this
series touches multiple subsystems, the situation is a bit tricky.

Regards,
Kuan-Wei