Re: [PATCH] rtc: rs5c372: Fix read the time from RTC is illegal When reading time from an uninitialized RTC chip, The value may be illegal

Nobuhiro Iwamatsu
2021-05-24T04:42:27Z

Hi,

2021年5月20日(木) 12:32 <qxj511mail@gmail.com>:
>
> From: qiuxiaojin <qiuxiaojin@cvte.com>

Please briefly describe the patch contained in the email to the subject.
And, please write a description of the patch in the text

>
> Signed-off-by: qiuxiaojin <qiuxiaojin@cvte.com>
> ---
> drivers/rtc/rtc-rs5c372.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/drivers/rtc/rtc-rs5c372.c b/drivers/rtc/rtc-rs5c372.c
> index 3bd6eaa0dcf6..ce61e15d5f3a 100644
> --- a/drivers/rtc/rtc-rs5c372.c
> +++ b/drivers/rtc/rtc-rs5c372.c
> @@ -212,6 +212,7 @@ static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
> struct rs5c372 *rs5c = i2c_get_clientdata(client);
> int status = rs5c_get_regs(rs5c);
> unsigned char ctrl2 = rs5c->regs[RS5C_REG_CTRL2];
> + int flags_utime = 0;
>
> if (status < 0)
> return status;
> @@ -239,12 +240,27 @@ static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
> tm->tm_wday = bcd2bin(rs5c->regs[RS5C372_REG_WDAY] & 0x07);
> tm->tm_mday = bcd2bin(rs5c->regs[RS5C372_REG_DAY] & 0x3f);
>
> + if (tm->tm_mday < 1) {
> + // The value read from the register may be zero, which is an illegal value

Please use C89 style commet (/* */).

> + flags_utime = flags_utime + 1;

I like using ++ (flags_utime++).

> + tm->tm_mday = 1;
> + }
> +
> /* tm->tm_mon is zero-based */
> tm->tm_mon = bcd2bin(rs5c->regs[RS5C372_REG_MONTH] & 0x1f) - 1;
>
> + if (tm->tm_mon < 0) {
> + flags_utime = flags_utime + 1;
> + tm->tm_mday = 0;
> + }
> +
> /* year is 1900 + tm->tm_year */
> tm->tm_year = bcd2bin(rs5c->regs[RS5C372_REG_YEAR]) + 100;
>
> + if (flags_utime > 0) {

{} is unnecessary.

> + rs5c372_rtc_set_time(dev, tm);

A build error will occur because there is no declaration of
rs5c372_rtc_set_time.
Please make sure this can be compiled.

> + }
> +
> dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
> "mday=%d, mon=%d, year=%d, wday=%d\n",
> __func__,
> --
> 2.29.0
>

--
Nobuhiro Iwamatsu
iwamatsu at {nigauri.org / debian.org}
GPG ID: 40AD1FA6