Re: [PATCH v7 2/6] rtc: s35390a: Add missing newline to dev_err

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] RTC_VL_READ ioctl clears low-voltage hardware flags without caching them, silently masking time corruption for subsequent reads.
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commit d2afec77b76a14e1c30b1da14673de2795a5f488
Author: Markus Probst <markus.probst@posteo.de>

rtc: s35390a: Add missing newline to dev_err

This commit adds a missing newline character to a dev_err() message
in the probe function of the s35390a RTC driver.

> diff --git a/drivers/rtc/rtc-s35390a.c b/drivers/rtc/rtc-s35390a.c
> index b72eef4fb0997..4cfe7034c5165 100644
> --- a/drivers/rtc/rtc-s35390a.c
> +++ b/drivers/rtc/rtc-s35390a.c
> @@ -494,7 +494,7 @@ static int s35390a_probe(struct i2c_client *client)
>  		buf = 0;
>  		err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &buf, 1);
>  		if (err < 0) {
> -			dev_err(dev, "error disabling alarm");
> +			dev_err(dev, "error disabling alarm\n");
>  			return err;
>  		}
>  	} else {

[Severity: High]
This isn't a bug introduced by this patch, but while reviewing this file,
I noticed a potential issue with how power-loss events are handled.

Does the RTC_VL_READ ioctl clear the low-voltage hardware flags without caching
them?

Looking at s35390a_rtc_ioctl() in drivers/rtc/rtc-s35390a.c:

	case RTC_VL_READ:
		/* s35390a_reset set lowvoltage flag and init RTC if needed */
		err = s35390a_read_status(s35390a, &sts);
		if (err < 0)
			return err;
		if (copy_to_user((void __user *)arg, &err, sizeof(int)))

It appears s35390a_read_status() reads the hardware status register, which 
automatically clears the low voltage flags in the hardware upon reading.

Because the driver does not cache this state or reinitialize the chip to a known
state, the hardware permanently forgets that a power loss occurred.

Will a subsequent call to read the time via s35390a_rtc_read_time() read
the status register, receive no error, and silently return corrupted or 
uninitialized time data to userspace instead of returning an error?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260829-rtc_s35390a_int1-v7-0-debcd31143ae@posteo.de?part=2