Date:   Mon, 22 Nov 2021 13:03:25 +0200
From:   Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
To:     Matti Vaittinen <mazziesaccount@gmail.com>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Cc:     Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jiri Kosina <trivial@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Yury Norov <yury.norov@gmail.com>,
        Kumar Kartikeya Dwivedi <memxor@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/4] bitops: Add single_bit_set()
Message-ID: <73d5e4286282a47b614d1cc5631eb9ff2a7e2b44.1637330431.git.matti.vaittinen@fi.rohmeurope.com>
References: <cover.1637330431.git.matti.vaittinen@fi.rohmeurope.com>
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There are cases when it is useful to check a bit-mask has only one bit
set. Add a generic helper for it instead of baking own one for each
user.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
---
I am not at all sure what would be the best place for this. Please let
me know if you think some other file would be more appropriate.
---
 include/linux/bitops.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5e62e2383b7f..dd6c7baed3d3 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -66,6 +66,26 @@ extern unsigned long __sw_hweight64(__u64 w);
 	     (start) < (size); \
 	     (start) =3D find_next_clump8(&(clump), (bits), (size), (start) + 8))
=20
+/**
+ * single_bit_set - check if only one bit is set in value
+ * @bits:		value to check
+ * @bits_to_check:	how many bits we should scan
+ *
+ * Return: true if only one of the checked bits is set, othervice return f=
alse.
+ */
+static inline bool single_bit_set(const unsigned long bits, int bits_to_ch=
eck)
+{
+	int bit;
+
+	bit =3D find_first_bit(&bits, bits_to_check);
+	if (bit =3D=3D bits_to_check)
+		return false;
+
+	bit =3D find_next_bit(&bits, bits_to_check, bit + 1);
+
+	return (bit =3D=3D bits_to_check);
+}
+
 static inline int get_bitmask_order(unsigned int count)
 {
 	int order;
--=20
2.31.1


--=20
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =3D]=20

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