+ iio-magnetometer-yas530-use-signed-integer-type-for-clamp-limits.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: iio: magnetometer: yas530: use signed integer type for clamp limits
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     iio-magnetometer-yas530-use-signed-integer-type-for-clamp-limits.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/iio-magnetometer-yas530-use-signed-integer-type-for-clamp-limits.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jakob Hauser <jahau@rocketmail.com>
Subject: iio: magnetometer: yas530: use signed integer type for clamp limits
Date: Fri, 29 Nov 2024 22:25:07 +0100

In the function yas537_measure() there is a clamp_val() with limits of
-BIT(13) and BIT(13) - 1.  The input clamp value h[] is of type s32.  The
BIT() is of type unsigned long integer due to its define in
include/vdso/bits.h.  The lower limit -BIT(13) is recognized as -8192 but
expressed as an unsigned long integer.  The size of an unsigned long
integer differs between 32-bit and 64-bit architectures.  Converting this
to type s32 may lead to undesired behavior.

Additionally, in the calculation lines h[0], h[1] and h[2] the unsigned
long integer divisor BIT(13) causes an unsigned division, shifting the
left-hand side of the equation back and forth, possibly ending up in large
positive values instead of negative values on 32-bit architectures.

To solve those two issues, declare a signed integer with a value of
BIT(13).

There is another omission in the clamp line: clamp_val() returns a value
and it's going nowhere here.  Self-assign it to h[i] to make use of the
clamp macro.

Finally, replace clamp_val() macro by clamp() because after changing the
limits from type unsigned long integer to signed integer it's fine that
way.

Link: https://lkml.kernel.org/r/11609b2243c295d65ab4d47e78c239d61ad6be75.1732914810.git.jahau@rocketmail.com
Fixes: 65f79b501030 ("iio: magnetometer: yas530: Add YAS537 variant")
Signed-off-by: Jakob Hauser <jahau@rocketmail.com>

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202411230458.dhZwh3TT-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202411282222.oF0B4110-lkp@intel.com/
Cc: David Laight <david.laight@aculab.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/iio/magnetometer/yamaha-yas530.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/iio/magnetometer/yamaha-yas530.c~iio-magnetometer-yas530-use-signed-integer-type-for-clamp-limits
+++ a/drivers/iio/magnetometer/yamaha-yas530.c
@@ -372,6 +372,7 @@ static int yas537_measure(struct yas5xx
 	u8 data[8];
 	u16 xy1y2[3];
 	s32 h[3], s[3];
+	int half_range = BIT(13);
 	int i, ret;
 
 	mutex_lock(&yas5xx->lock);
@@ -406,13 +407,13 @@ static int yas537_measure(struct yas5xx
 	/* The second version of YAS537 needs to include calibration coefficients */
 	if (yas5xx->version == YAS537_VERSION_1) {
 		for (i = 0; i < 3; i++)
-			s[i] = xy1y2[i] - BIT(13);
-		h[0] = (c->k *   (128 * s[0] + c->a2 * s[1] + c->a3 * s[2])) / BIT(13);
-		h[1] = (c->k * (c->a4 * s[0] + c->a5 * s[1] + c->a6 * s[2])) / BIT(13);
-		h[2] = (c->k * (c->a7 * s[0] + c->a8 * s[1] + c->a9 * s[2])) / BIT(13);
+			s[i] = xy1y2[i] - half_range;
+		h[0] = (c->k *   (128 * s[0] + c->a2 * s[1] + c->a3 * s[2])) / half_range;
+		h[1] = (c->k * (c->a4 * s[0] + c->a5 * s[1] + c->a6 * s[2])) / half_range;
+		h[2] = (c->k * (c->a7 * s[0] + c->a8 * s[1] + c->a9 * s[2])) / half_range;
 		for (i = 0; i < 3; i++) {
-			clamp_val(h[i], -BIT(13), BIT(13) - 1);
-			xy1y2[i] = h[i] + BIT(13);
+			h[i] = clamp(h[i], -half_range, half_range - 1);
+			xy1y2[i] = h[i] + half_range;
 		}
 	}
 
_

Patches currently in -mm which might be from jahau@rocketmail.com are

iio-magnetometer-yas530-use-signed-integer-type-for-clamp-limits.patch