linux-kernel - Re: [PATCH 2/2] chipidea: Use devm_request

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Message-ID: <CAL411-qQm9vgDHswEM6PEvFKAaqd=e3qm-zViUbNztv0tJYa8Q@mail.gmail.com>
Date:	Wed, 31 Jul 2013 21:55:26 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	Tejun Heo <htejun@...il.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Peter Chen <peter.chen@...escale.com>,
	Fabio Estevam <festevam@...il.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	kernel@...gutronix.de,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Jeff Garzik <jeff@...zik.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org,
	Mike Turquette <mturquette@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] chipidea: Use devm_request_irq()

On Wed, Jul 31, 2013 at 9:27 PM, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Jul 31, 2013 at 07:55:27AM -0400, Tejun Heo wrote:
>
>> If you have DMA / IRQ / command engine deactivations in devm path
>> which often is the case with full conversions, freeing any resources
>> including DMA areas and host private data in the wrong order is a
>> horrible idea.  It's worse as it won't really be noticeable in most
>> cases.
>
> It's really only interrupts that affect most devices - if there's DMA or
> anything going on after the remove() then as you said earlier the driver
> is probably doing something wrong.

I think the main point is we should allocate managed resource which is used
at interrupt handler before devm_request_irq, and all resources used
at interrupt
handler should be managed.

If we use non-managed resource at interrupt handler, but using managed interrupt
handler, things still will go wrong if there is an odd (unexpected)
interrupt after
we finish deactivation at removal.

-- 
BR,
Peter Chen
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