linux-kernel - Re: [rtc-linux] [PATCH 04/10] RTC: Cleanup rtc_class_ops->read

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Message-ID: <20110222181647.GA25569@opensource.wolfsonmicro.com>
Date:	Tue, 22 Feb 2011 10:16:48 -0800
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	john stultz <johnstul@...ibm.com>
Cc:	rtc-linux@...glegroups.com, LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Marcelo Roberto Jimenez <mroberto@...i.cetuc.puc-rio.br>
Subject: Re: [rtc-linux] [PATCH 04/10] RTC: Cleanup
 rtc_class_ops->read_alarm()

On Tue, Feb 22, 2011 at 12:09:38AM -0800, john stultz wrote:

> Just so I can better get a grip of the cases your considering, could you
> maybe give me some more detailed examples of where you'd like to see the
> alarm timer be set and then persist across multiple power cycles before
> firing? And how is that persistent value managed by the application
> setting it?

The WM83xx RTCs can do this (the alarm can be used to initiate a boot)
and I'd expect many embedded RTC controllers can do similar.  The
application would manage this by owning the RTC in the system, usually
with a configuration saying something like "boot every day at 7am" or
something.

Having thought about this a bit I'm thinking that this sort of alarm
handling is probably something I'd expect to see handled in userspace.
I can see us providing a virtual RTC driver that can generate alarms
when there's no actual RTC hardware but adding additional functionality
on top of the hardware feels like an application issue.
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