linux-kernel - 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

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Date:   Mon, 24 May 2021 13:40:48 +0900
From:   Nobuhiro Iwamatsu <iwamatsu@...auri.org>
To:     qxj511mail@...il.com
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-rtc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        qiuxiaojin@...e.com
Subject: 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

Hi,

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