linux-kernel - Re: [PATCH 4/4] timers: posix interface for alarm-timers

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Date:	Wed, 20 Apr 2011 08:34:26 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	linux-kernel@...r.kernel.org,
	Arve Hjønnevåg <arve@...roid.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>
Subject: Re: [PATCH 4/4] timers: posix interface for alarm-timers

On Tue, Apr 19, 2011 at 04:58:30PM -0700, John Stultz wrote:
> This patch exposes alarm-timers to userland via the posix clock
> and timers interface, using two new clockids: CLOCK_REALTIME_ALARM
> and CLOCK_BOOTTIME_ALARM. Both clockids behave identically to
> CLOCK_REALTIME and CLOCK_BOOTTIME, respectively, but timers
> set against the _ALARM suffixed clockids will wake the system if
> it is suspended.

So, is there reason these cannot or should not be using the dynamic
posix clock interface?

> The semantics of the Android alarm driver are different from what
> this posix interface provides.
...
> One potential way to implement similar semantics may be via
> the timerfd infrastructure, but this needs more research.
> 
> There may also need to be some sort of sysfs system level policy
> hooks that allow alarm timers to be disabled to keep them
> from firing at inappropriate times (ie: laptop in a well insulated
> bag, mid-flight).

I have not put hardly any thought into these issues, but the dynamic
interface gives you a character device at no extra charge.

Richard
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