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From:   Sebastian Reichel <sebastian.reichel@collabora.com>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        David Laight <David.Laight@ACULAB.COM>,
        linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Vasily Gorbik <gor@linux.ibm.com>,
        Niklas Schnelle <schnelle@linux.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sebastian Reichel <sebastian.reichel@collabora.com>,
        kernel@collabora.com
Subject: [PATCH v4 1/3] math.h: add DIV_ROUND_UP_NO_OVERFLOW
Date:   Tue, 24 Oct 2023 18:18:15 +0200
Message-ID: <20231024161931.78567-2-sebastian.reichel@collabora.com>
In-Reply-To: <20231024161931.78567-1-sebastian.reichel@collabora.com>
References: <20231024161931.78567-1-sebastian.reichel@collabora.com>
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Add a new DIV_ROUND_UP helper, which cannot overflow when
big numbers are being used.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 include/linux/math.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/math.h b/include/linux/math.h
index dd4152711de7..f80bfb375ab9 100644
--- a/include/linux/math.h
+++ b/include/linux/math.h
@@ -36,6 +36,17 @@
 
 #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
 
+/**
+ * DIV_ROUND_UP_NO_OVERFLOW - divide two numbers and always round up
+ * @n: numerator / dividend
+ * @d: denominator / divisor
+ *
+ * This functions does the same as DIV_ROUND_UP, but internally uses a
+ * division and a modulo operation instead of math tricks. This way it
+ * avoids overflowing when handling big numbers.
+ */
+#define DIV_ROUND_UP_NO_OVERFLOW(n, d) (((n) / (d)) + !!((n) % (d)))
+
 #define DIV_ROUND_DOWN_ULL(ll, d) \
 	({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })
 
-- 
2.42.0