linux-kernel - [PATCH next v4 1/5] minmax: Add umin(a, b) and umax(a, b)

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Message-ID: <41d93ca827a248698ec64bf57e0c05a5@AcuMS.aculab.com>
Date:   Mon, 18 Sep 2023 08:16:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>,
        'Andrew Morton' <akpm@...ux-foundation.org>,
        "'Matthew Wilcox (Oracle)'" <willy@...radead.org>,
        'Christoph Hellwig' <hch@...radead.org>,
        "'Jason A. Donenfeld'" <Jason@...c4.com>
Subject: [PATCH next v4 1/5] minmax: Add umin(a, b) and umax(a, b)

These can be used when min()/max() errors a signed v unsigned
compare when the signed value is known to be non-negative.

Unlike min_t(some_unsigned_type, a, b) umin() will never
mask off high bits if an inappropriate type is selected.

The '+ 0u + 0ul + 0ull' may look strange.
The '+ 0u' is needed for 'signed int' on 64bit systems.
The '+ 0ul' is needed for 'signed long' on 32bit systems.
The '+ 0ull' is needed for 'signed long long'.

Signed-off-by: David Laight <david.laight@...lab.com>
--
v4: Rename (from min_unsigned) to shorten code lines.
    Suggested by Linus.
v3: No change.
v2: Updated commit message.
---
 include/linux/minmax.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 83aebc244cba..0e89c78810f6 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -74,6 +74,23 @@
  */
 #define max(x, y)	__careful_cmp(x, y, >)
 
+/**
+ * umin - return minimum of two non-negative values
+ *   Signed types are zero extended to match a larger unsigned type.
+ * @x: first value
+ * @y: second value
+ */
+#define umin(x, y)	\
+	__careful_cmp((x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull, <)
+
+/**
+ * umax - return maximum of two non-negative values
+ * @x: first value
+ * @y: second value
+ */
+#define umax(x, y)	\
+	__careful_cmp((x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull, >)
+
 /**
  * min3 - return minimum of three values
  * @x: first value
-- 
2.17.1

-
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