linux-kernel - Re: [PATCH] rtc-dev: stop periodic interrupts on device release

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Date:	Sat, 26 Jul 2008 23:03:57 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"David Brownell" <david-b@...bell.net>
Cc:	"Tomas Janousek" <tomi@...i.cz>, linux-kernel@...r.kernel.org,
	"Alessandro Zummo" <alessandro.zummo@...ertech.it>
Subject: Re: [PATCH] rtc-dev: stop periodic interrupts on device release

On Sat, Jul 26, 2008 at 4:50 PM, David Brownell wrote:
> On Saturday 26 July 2008, Tomas Janousek wrote:
>> I am aware that some drivers, like rtc-sh, handle userspace PIE sets in their
>> ioctl op, exporting the irq_set_state op at the same time. The logic in
>> rtc_irq_set_state should make sure it doesn't matter and the driver should not
>> need to care stopping periodic interrupts in its release routine any more.
>> I did not look at other drivers though.
>
> A quick grep shows that out of 42 (wow!) current RTC drivers:
>
>  - rtc-{bfin,sa1100,sh,test} support ioctl(PIE_ON/PIE_OFF), at least
>   before some recent patches fixing that glitch (not in my tree) by
>   switching to irq_set_state().

the rtc-bfin.c patches are in some queue somewhere to fix this ;)

>  - Of those:  rtc-{bfin,s3c,sa1100,sh,vr41xx} all have release()
>   methods ... though it looks to me like most of those wrongly
>   disable *all* IRQs, even ones in use by something other than
>   the /dev client closing that FD.

rtc-bfin.c turns off all irqs and frees it in the release() function
(since the irq is requested in the open() function).  i guess that
isnt supposed to happen huh.

> That suggests there's quite a mess yet to be fixed.  This patch
> will ensure that periodic IRQs get properly shut off by close()
> or exit() of a task that started them.  Those release() methods
> shouldn't then be second-guessing things.
>
> And then there are the other two types of IRQ.  Update IRQs can
> only be enabled through ioctl(UIE_ON), so they're fair game to
> turn off when closing /dev files.  Alarms seem to be a special
> case -- best not touched when closing files.

specific drivers shouldnt worry about this then right ?  handle it in rtc-dev ?
-mike
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