linux-kernel - Re: [PATCH] alarmtimer: check RTC features instead of ops

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Message-ID: <877dkkfdif.ffs@nanos.tec.linutronix.de>
Date:   Fri, 30 Apr 2021 09:16:40 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] alarmtimer: check RTC features instead of ops

On Thu, Apr 29 2021 at 23:49, Alexandre Belloni wrote:
> Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to know whether
> alarms are available.
>
> Fixes: 7ae41220ef58 ("rtc: introduce features bitfield")
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
> ---
> Hello,
>
> This doesn't seem much but this solve an issue where following a change in the
> RTC driver, this part of the code will think the RTC is alarm capable while it
> is not, then breaking the alarmtimer functionnality.

So a driver has the set_alarm() callback but does not advertise
RTC_FEATURE_ALARM for whatever reason and why ever this makes sense.

I don't mind the patch, but the changelog is a bit meager in explaining
the WHY.

Thanks,

        tglx