linux-kernel - [PATCH 1/7] math64: Add div64_s64

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Message-Id: <20250715012023.2050178-2-sean.anderson@linux.dev>
Date: Mon, 14 Jul 2025 21:20:17 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Jonathan Cameron <jic23@...nel.org>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-iio@...r.kernel.org,
	linux-hwmon@...r.kernel.org
Cc: Andy Shevchenko <andy@...nel.org>,
	Nuno Sá <nuno.sa@...log.com>,
	linux-kernel@...r.kernel.org,
	David Lechner <dlechner@...libre.com>,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH 1/7] math64: Add div64_s64_rem

Add a function to do signed 64-bit division with remainder. This is
implemented using div64_u64_rem in the same way that div_s64_rem is
implemented using div_u64_rem.

Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---

 include/linux/math64.h | 18 ++++++++++++++++++
 lib/math/div64.c       | 20 ++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index 6aaccc1626ab..0a414446af89 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -57,6 +57,20 @@ static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
 	return dividend / divisor;
 }
 
+/**
+ * div64_s64_rem - signed 64bit divide with 64bit divisor and remainder
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 64bit divisor
+ * @remainder: pointer to signed 64bit remainder
+ *
+ * Return: sets ``*remainder``, then returns dividend / divisor
+ */
+static inline s64 div64_s64_rem(s64 dividend, s64 divisor, s64 *remainder)
+{
+	*remainder = dividend % divisor;
+	return dividend / divisor;
+}
+
 /**
  * div64_u64 - unsigned 64bit divide with 64bit divisor
  * @dividend: unsigned 64bit dividend
@@ -102,6 +116,10 @@ extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
 extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder);
 #endif
 
+#ifndef div64_s64_rem
+s64 div64_s64_rem(s64 dividend, s64 divisor, s64 *remainder);
+#endif
+
 #ifndef div64_u64
 extern u64 div64_u64(u64 dividend, u64 divisor);
 #endif
diff --git a/lib/math/div64.c b/lib/math/div64.c
index 5faa29208bdb..ccef0db85681 100644
--- a/lib/math/div64.c
+++ b/lib/math/div64.c
@@ -124,6 +124,26 @@ u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
 EXPORT_SYMBOL(div64_u64_rem);
 #endif
 
+#ifndef div_s64_rem
+s64 div64_s64_rem(s64 dividend, s64 divisor, s64 *remainder)
+{
+	u64 quotient;
+
+	if (dividend < 0) {
+		quotient = div64_u64_rem(-dividend, abs(divisor), (u64 *)remainder);
+		*remainder = -*remainder;
+		if (divisor > 0)
+			quotient = -quotient;
+	} else {
+		quotient = div64_u64_rem(dividend, abs(divisor), (u64 *)remainder);
+		if (divisor < 0)
+			quotient = -quotient;
+	}
+	return quotient;
+}
+EXPORT_SYMBOL(div64_s64_rem);
+#endif
+
 /*
  * div64_u64 - unsigned 64bit divide with 64bit divisor
  * @dividend:	64bit dividend
-- 
2.35.1.1320.gc452695387.dirty