linux-kernel - Re: [PATCH 2/2] iio: ti_am335x_adc: Add continuous sampling support

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Message-ID: <20130919051611.GA4363@gmail.com>
Date:	Thu, 19 Sep 2013 10:16:12 +0500
From:	"Zubair Lutfullah :" <zubair.lutfullah@...il.com>
To:	Jonathan Cameron <jic23@...nel.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Zubair Lutfullah :" <zubair.lutfullah@...il.com>,
	linux-iio@...r.kernel.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, bigeasy@...utronix.de,
	gregkh@...uxfoundation.org
Subject: Re: [PATCH 2/2] iio: ti_am335x_adc: Add continuous sampling support

On Wed, Sep 18, 2013 at 06:05:12PM +0100, Jonathan Cameron wrote:
> 
> >> >However in this case such conversion us dangerous. With all but IRQ
> >> >resource managed by the traditional methods they will be released
> >first
> >> >with IRQ handler deregistered very last. Therefore if device is not
> >> >properly quiesced IRQ raised during driver unbinding is likely to
> >> >result
> >> >in kernel oops.
> >> >
> >> >IOW devm_request_irq() is very often evil (it is still useful if
> >_all_
> >> >your resources are managed by devm_*).
> >> >
> >> >In case of your driver I'd recommend switching to
> >> >request_irq()/free_irq() instead.
> >> >
> >> >Thanks.
> >> 
> >> Pretty much all resources are devm managed in here
> >> 
> >>
> >https://git.kernel.org/cgit/linux/kernel/git/jic23/iio.git/tree/drivers/iio/adc/ti_am335x_adc.c?h=togreg&id=7a1aeba7ed0d5a1e83fd5a8ee2a2869430d40347
> >
> >
> >So we are guaranteed that that new kfifo that is being allocated just
> >before we requesting IRQ and will be freed way before we free the IRQ
> >will not be used by the IOTQ handler?
> >
> >Thanks.
> Good point. I forgot about that.  The source of interrupts 'should' be disabled before the kfifo is freed but I guess perhaps better to play it safe. Would take a fair bit of review to be sure that is not going to cause grief.
> 
> A few more devm handlers need writing before it is truly useful here.
> 
> Thanks for pointing this out.
> 
> J

If I understand the conclusion correctly, no devm here?

Zubair
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