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hwmon: (ltc2991) Fix mixed signed/unsigned in DIV_ROUND_CLOSEST

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Fix use of DIV_ROUND_CLOSEST where a possibly negative value is divided
by an unsigned type by casting the unsigned type to the signed type of
the same size (st->r_sense_uohm[channel] has type of u32).

The docs on the DIV_ROUND_CLOSEST macro explain that dividing a negative
value by an unsigned type is undefined behavior. The actual behavior is
that it converts both values to unsigned before doing the division, for
example:

    int ret = DIV_ROUND_CLOSEST(-100, 3U);

results in ret == 1431655732 instead of -33.

Fixes: 2b9ea4262a ("hwmon: Add driver for ltc2991")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20250115-hwmon-ltc2991-fix-div-round-closest-v1-1-b4929667e457@baylibre.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
David Lechner 2025-01-15 14:48:27 -06:00 committed by Guenter Roeck
parent b46ba47d7b
commit e9b24deb84
1 changed files with 1 additions and 1 deletions
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2
drivers/hwmon/ltc2991.c
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@ -125,7 +125,7 @@ static int ltc2991_get_curr(struct ltc2991_state *st, u32 reg, int channel,
/* Vx-Vy, 19.075uV/LSB */
*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 19075,
st->r_sense_uohm[channel]);
(s32)st->r_sense_uohm[channel]);
return 0;
}