linux-kernel - Re: [PATCH V2] drivers/rtc/rtc-ds1307.c: Enable the mcp794xx alarm after programming time

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150422113053.GI8539@piout.net>
Date:	Wed, 22 Apr 2015 13:30:53 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Nishanth Menon <nm@...com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH V2] drivers/rtc/rtc-ds1307.c: Enable the mcp794xx alarm
 after programming time

On 21/04/2015 at 20:59:15 -0500, Nishanth Menon wrote :
> >> Why is that so? when set alarm is requested for time X, you want
> >> interrupt at time X, not an interrupt for previous configured RTC
> >> alarm time!
> >>
> > 
> > You expect at least an interrupt.
> 
> And you will get an interrupt if the event occurs before the i2c burst
> starts. Once the i2cburst does start, you are committing to the new time.
> 

You mean that even if ALM0EN is set after ALM0IF was set to 1, it will
trigger the interrupt? I had a look at the MFP output block diagram
would let me think that this is the case. I was thinking otherwise
before. If that is so, then indeed, your patch is OK.

My concern was about the time between ds1307->write_block_data() and
i2c_smbus_write_byte_data() which actually calls cond_sched().

I fully agree that your patch doesn't change the behaviour for the other
cases you presented and further clean up is to be done in a separate set
of patches.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/