linux-kernel - Re: [PATCH 1/4] rtc: sa1100: enable/disable rtc when probe/remove the device

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Date:	Mon, 3 Dec 2012 09:39:37 +0800
From:	Chao Xie <xiechao.mail@...il.com>
To:	Haojian Zhuang <haojian.zhuang@...il.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Chao Xie <chao.xie@...vell.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/4] rtc: sa1100: enable/disable rtc when probe/remove the device

On Fri, Nov 30, 2012 at 3:04 PM, Haojian Zhuang
<haojian.zhuang@...il.com> wrote:
> On Thu, Nov 29, 2012 at 6:25 PM, Russell King - ARM Linux
> <linux@....linux.org.uk> wrote:
>> On Wed, Nov 28, 2012 at 09:21:07PM -0500, Chao Xie wrote:
>>> The original sa1100_rtc_open/sa1100_rtc_release will be called
>>> when the /dev/rtc0 is opened or closed.
>>> In fact, these two functions will enable/disable the clock, and
>>> register/unregister the irqs.
>>> User application will use /dev/rtc0 to read the rtc time or set
>>> the alarm. The rtc should still run indepent of open/close the
>>> rtc device.
>>> So only enable clock and register the irqs when probe the device,
>>> and disable clock and unregister the irqs when remove the device.
>>
>> NAK.  I don't think you properly understand what's going on here if you
>> think moving the entire open and release functions into the probe and
>> remove functions is the right thing to do.
>
> Since PXA27x & PXA3xx supports dual rtc device at the same time,
> user could choose use either of rtc at run time. Then clk & irq are setup
> in open().
>
> Chao,
> So you shouldn't remove them into probe().

How can user to choose one RTC?
The user API, for example "date" will open the device, get the time
and then close the device.
WHen set a alarm, it is the same routine. open->set->close.
The open routine will enable clock and register irq, close will
disable the clock and unregister irq. It means that if only open is
invoked, rtc begins to work, and after close is invoked rtc stops
working. It means that the user can not get correct time and can not
get right alarm.
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