linux-kernel - [PATCH v2 18/20] linux/power_of_2.h: Add __IS_POWER_OF_2(n) and __IS_POWER_OF_2_OR

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Message-Id: <20211120130104.185699-20-alx.manpages@gmail.com>
Date:   Sat, 20 Nov 2021 14:01:02 +0100
From:   Alejandro Colomar <alx.manpages@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Alejandro Colomar <alx.manpages@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Kees Cook <keescook@...omium.org>,
        Joe Perches <joe@...ches.com>
Subject: [PATCH v2 18/20] linux/power_of_2.h: Add __IS_POWER_OF_2(n) and __IS_POWER_OF_2_OR_0(n) macros

Tested:

$ cat pow2.c
 #include <stdio.h>

 #define is_power_of_2_or_0(n)  (((n) & ((n) - 1)) == 0)
 #define is_power_of_2(n)       (is_power_of_2_or_0(n) && ((n) != 0))

int main(void)
{
	printf("%i, %i, %i\n", 8, is_power_of_2_or_0(8), is_power_of_2(8));
	printf("%i, %i, %i\n", 7, is_power_of_2_or_0(7), is_power_of_2(7));
	printf("%i, %i, %i\n", 6, is_power_of_2_or_0(6), is_power_of_2(6));
	printf("%i, %i, %i\n", 5, is_power_of_2_or_0(5), is_power_of_2(5));
	printf("%i, %i, %i\n", 4, is_power_of_2_or_0(4), is_power_of_2(4));
	printf("%i, %i, %i\n", 3, is_power_of_2_or_0(3), is_power_of_2(3));
	printf("%i, %i, %i\n", 2, is_power_of_2_or_0(2), is_power_of_2(2));
	printf("%i, %i, %i\n", 1, is_power_of_2_or_0(1), is_power_of_2(1));
	printf("%i, %i, %i\n", 0, is_power_of_2_or_0(0), is_power_of_2(0));
}

$ cc pow2.c
$ ./a.out
8, 1, 1
7, 0, 0
6, 0, 0
5, 0, 0
4, 1, 1
3, 0, 0
2, 1, 1
1, 1, 1
0, 1, 0

Signed-off-by: Alejandro Colomar <alx.manpages@...il.com>
---
 include/linux/power_of_2.h | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 include/linux/power_of_2.h

diff --git a/include/linux/power_of_2.h b/include/linux/power_of_2.h
new file mode 100644
index 000000000000..812fe86eefcd
--- /dev/null
+++ b/include/linux/power_of_2.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_POWER_OF_2_H
+#define _LINUX_POWER_OF_2_H
+
+
+#define __IS_POWER_OF_2_OR_0(n)  (((n) & ((n) - 1)) == 0)
+#define __IS_POWER_OF_2(n)       (__IS_POWER_OF_2_OR_0(n) && ((n) != 0))
+
+
+#endif	/* _LINUX_POWER_OF_2_H */
-- 
2.33.1