[PATCH] rtc: ds1307: Check the calibration register read result

[PATCH] rtc: ds1307: Check the calibration register read result

[Zhu Jun]

m41txx_rtc_read_offset() ignores regmap_read() failures and calculates
the calibration offset from an uninitialized control register value.
An I2C transfer error can therefore be reported as a successful offset
read with an arbitrary result.

Return the read error before decoding the register or updating the
caller's offset.

Fixes: 79230ff64167 ("rtc: ds1307: add offset sysfs for mt41txx chips.")
Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
---
 drivers/rtc/rtc-ds1307.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 8ab28cc2f181..2e9f0b3d2a93 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -853,9 +853,12 @@ static int m41txx_rtc_read_offset(struct device *dev, long *offset)
 {
 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
 	unsigned int ctrl_reg;
+	int ret;
 	u8 val;
 
-	regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
+	ret = regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
+	if (ret)
+		return ret;
 
 	val = ctrl_reg & M41TXX_M_CALIBRATION;
 
-- 
2.51.0

Re: [PATCH] rtc: ds1307: Check the calibration register read result

[sashiko-bot]

> m41txx_rtc_read_offset() ignores regmap_read() failures and calculates
> the calibration offset from an uninitialized control register value.
> An I2C transfer error can therefore be reported as a successful offset
> read with an arbitrary result.
> 
> Return the read error before decoding the register or updating the
> caller's offset.
> 
> Fixes: 79230ff64167 ("rtc: ds1307: add offset sysfs for mt41txx chips.")
> Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112071627.154412-1-zhujun2@cmss.chinamobile.com?part=1