On Tue, Oct 1, 2019 at 12:53 PM Alexandre Belloni
<alexandre.belloni@xxxxxxxxxxx> wrote:
>
> Hi Nick,
>
> On 25/09/2019 14:32:09-0600, Nick Crews wrote:
> > If the RTC HW returns an invalid time, the rtc_year_days()
> > call would crash. This patch adds error logging in this
> > situation, and removes the tm_yday and tm_wday calculations.
> > These fields should not be relied upon by userspace
> > according to man rtc, and thus we don't need to calculate
> > them.
> >
> > Signed-off-by: Nick Crews <ncrews@xxxxxxxxxxxx>
> > ---
> > drivers/rtc/rtc-wilco-ec.c | 13 +++++++++----
> > 1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
> > index 8ad4c4e6d557..53da355d996a 100644
> > --- a/drivers/rtc/rtc-wilco-ec.c
> > +++ b/drivers/rtc/rtc-wilco-ec.c
> > @@ -110,10 +110,15 @@ static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
> > tm->tm_mday = rtc.day;
> > tm->tm_mon = rtc.month - 1;
> > tm->tm_year = rtc.year + (rtc.century * 100) - 1900;
> > - tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
> > -
> > - /* Don't compute day of week, we don't need it. */
> > - tm->tm_wday = -1;
> > + /* Ignore other tm fields, man rtc says userspace shouldn't use them. */
> > +
> > + if (rtc_valid_tm(tm)) {
> > + dev_err(dev,
> > + "Time from RTC is invalid: second=%u, minute=%u, hour=%u, day=%u, month=%u, year=%u, century=%u",
> > + rtc.second, rtc.minute, rtc.hour, rtc.day, rtc.month,
> > + rtc.year, rtc.century);
>
> Do you mind using %ptR? At this point you already filled the tm struct
> anyway and if you print century separately, you can infer tm_year.
I do not think this is a good idea: we have just established that tm
does not contain valid data. Does %ptR guarantee that it handles junk
better than, let's say, rtc_year_days(), and does not crash when
presented with garbage?
Thanks,
Dmitry
