linux-kernel - [PATCH] rtc: pcf2123: fix negative offset rounding

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Date:   Wed, 19 Jun 2019 15:17:53 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     linux-rtc@...r.kernel.org
Cc:     Dylan Howey <Dylan.Howey@...nantco.com>,
        linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH] rtc: pcf2123: fix negative offset rounding

Using result = (value + divisor/2) / divisor is rounding values up and only
works well for positive values. Instead use DIV_ROUND_CLOSEST which does
the correct thing.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/rtc/rtc-pcf2123.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-pcf2123.c b/drivers/rtc/rtc-pcf2123.c
index 39da8b214275..80a53d2dc813 100644
--- a/drivers/rtc/rtc-pcf2123.c
+++ b/drivers/rtc/rtc-pcf2123.c
@@ -244,7 +244,7 @@ static int pcf2123_set_offset(struct device *dev, long offset)
 	else if (offset < OFFSET_STEP * -128)
 		reg = -128;
 	else
-		reg = (s8)((offset + (OFFSET_STEP >> 1)) / OFFSET_STEP);
+		reg = DIV_ROUND_CLOSEST(offset, OFFSET_STEP);
 
 	/* choose fine offset only for odd values in the normal range */
 	if (reg & 1 && reg <= 63 && reg >= -64) {
-- 
2.21.0