This is a note to let you know that I've just added the patch titled
minmax.h: simplify the variants of clamp()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
minmax.h-simplify-the-variants-of-clamp.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From [email protected] Wed Oct 8 17:35:26 2025
From: Eliav Farber <[email protected]>
Date: Wed, 8 Oct 2025 15:29:43 +0000
Subject: minmax.h: simplify the variants of clamp()
To: <[email protected]>, <[email protected]>, <[email protected]>,
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ists.freedesktop.org>, <[email protected]>,
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Cc: Arnd Bergmann <[email protected]>, Christoph Hellwig <[email protected]>,
Dan Carpenter <[email protected]>, "Jason A. Donenfeld"
<[email protected]>, Jens Axboe <[email protected]>, Lorenzo Stoakes
<[email protected]>, Mateusz Guzik <[email protected]>, "Pedro
Falcato" <[email protected]>
Message-ID: <[email protected]>
From: David Laight <[email protected]>
[ Upstream commit 495bba17cdf95e9703af1b8ef773c55ef0dfe703 ]
Always pass a 'type' through to __clamp_once(), pass '__auto_type' from
clamp() itself.
The expansion of __types_ok3() is reasonable so it isn't worth the added
complexity of avoiding it when a fixed type is used for all three values.
Link:
https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Laight <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Jason A. Donenfeld <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Pedro Falcato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Eliav Farber <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
include/linux/minmax.h | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -183,29 +183,29 @@
#define __clamp(val, lo, hi) \
((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val)))
-#define __clamp_once(val, lo, hi, uval, ulo, uhi) ({
\
- __auto_type uval = (val);
\
- __auto_type ulo = (lo);
\
- __auto_type uhi = (hi);
\
+#define __clamp_once(type, val, lo, hi, uval, ulo, uhi) ({
\
+ type uval = (val);
\
+ type ulo = (lo);
\
+ type uhi = (hi);
\
BUILD_BUG_ON_MSG(statically_true(ulo > uhi),
\
"clamp() low limit " #lo " greater than high limit " #hi);
\
BUILD_BUG_ON_MSG(!__types_ok3(uval, ulo, uhi),
\
"clamp("#val", "#lo", "#hi") signedness error");
\
__clamp(uval, ulo, uhi); })
-#define __careful_clamp(val, lo, hi) \
- __clamp_once(val, lo, hi, __UNIQUE_ID(v_), __UNIQUE_ID(l_),
__UNIQUE_ID(h_))
+#define __careful_clamp(type, val, lo, hi) \
+ __clamp_once(type, val, lo, hi, __UNIQUE_ID(v_), __UNIQUE_ID(l_),
__UNIQUE_ID(h_))
/**
- * clamp - return a value clamped to a given range with strict typechecking
+ * clamp - return a value clamped to a given range with typechecking
* @val: current value
* @lo: lowest allowable value
* @hi: highest allowable value
*
- * This macro does strict typechecking of @lo/@hi to make sure they are of the
- * same type as @val. See the unnecessary pointer comparisons.
+ * This macro checks @val/@lo/@hi to make sure they have compatible
+ * signedness.
*/
-#define clamp(val, lo, hi) __careful_clamp(val, lo, hi)
+#define clamp(val, lo, hi) __careful_clamp(__auto_type, val, lo, hi)
/**
* clamp_t - return a value clamped to a given range using a given type
@@ -217,7 +217,7 @@
* This macro does no typechecking and uses temporary variables of type
* @type to make all the comparisons.
*/
-#define clamp_t(type, val, lo, hi) __careful_clamp((type)(val), (type)(lo),
(type)(hi))
+#define clamp_t(type, val, lo, hi) __careful_clamp(type, val, lo, hi)
/**
* clamp_val - return a value clamped to a given range using val's type
@@ -230,7 +230,7 @@
* type and @lo and @hi are literals that will otherwise be assigned a signed
* integer type.
*/
-#define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
+#define clamp_val(val, lo, hi) __careful_clamp(typeof(val), val, lo, hi)
/*
* Do not check the array parameter using __must_be_array().
Patches currently in stable-queue which might be from [email protected] are
queue-5.15/minmax-add-a-few-more-min_t-max_t-users.patch
queue-5.15/minmax-improve-macro-expansion-and-type-checking.patch
queue-5.15/minmax-fix-indentation-of-__cmp_once-and-__clamp_once.patch
queue-5.15/minmax.h-simplify-the-variants-of-clamp.patch
queue-5.15/minmax-add-in_range-macro.patch
queue-5.15/minmax.h-move-all-the-clamp-definitions-after-the-min-max-ones.patch
queue-5.15/minmax-don-t-use-max-in-situations-that-want-a-c-constant-expression.patch
queue-5.15/minmax.h-remove-some-defines-that-are-only-expanded-once.patch
queue-5.15/minmax.h-use-build_bug_on_msg-for-the-lo-hi-test-in-clamp.patch
queue-5.15/minmax-simplify-min-max-clamp-implementation.patch
queue-5.15/minmax-deduplicate-__unconst_integer_typeof.patch
queue-5.15/minmax-simplify-and-clarify-min_t-max_t-implementation.patch
queue-5.15/minmax.h-add-whitespace-around-operators-and-after-commas.patch
queue-5.15/minmax-avoid-overly-complicated-constant-expressions-in-vm-code.patch
queue-5.15/minmax-make-generic-min-and-max-macros-available-everywhere.patch
queue-5.15/minmax-fix-up-min3-and-max3-too.patch
queue-5.15/minmax.h-reduce-the-define-expansion-of-min-max-and-clamp.patch
queue-5.15/minmax-introduce-min-max-_array.patch
queue-5.15/minmax.h-update-some-comments.patch
