linux-kernel - Re: [PATCH 4.19 177/639] rtc: ds1307: rx8130: Fix alarm handling

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Message-ID: <20200125133036.GD14064@duo.ucw.cz>
Date:   Sat, 25 Jan 2020 14:30:36 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 177/639] rtc: ds1307: rx8130: Fix alarm handling

Hi!

> When the EXTENSION.WADA bit is set, register 0x19 contains a bitmap of
> week days, not a day of month. As Linux only handles a single alarm
> without repetition using day of month is more flexible, so clear this
> bit. (Otherwise a value depending on time.tm_wday would have to be
> written to register 0x19.)

So the comment explains why WADA bit needs to be clear.

> @@ -749,8 +749,8 @@ static int rx8130_set_alarm(struct device *dev, struct rtc_wkalrm *t)
>  	if (ret < 0)
>  		return ret;
>  
> -	ctl[0] &= ~RX8130_REG_EXTENSION_WADA;
> +	ctl[0] &= RX8130_REG_EXTENSION_WADA;

But then code is changed to preserve WADA bit while it was clearing it
before.

What is going on here?

Given WADA bit is already clear, is it -stable material?

Best regards,
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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