linux-kernel - Re: [PATCH] Input: introduce managed input devices (add devres support)

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Message-ID: <5132958.JXBGbd4rj1@dtor-d630.eng.vmware.com>
Date:	Wed, 31 Oct 2012 14:37:01 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: introduce managed input devices (add devres support)

On Wednesday, October 31, 2012 02:05:32 PM Tejun Heo wrote:
> Hello, Dmitry.
> 
> On Mon, Oct 22, 2012 at 10:35:14PM -0700, Dmitry Torokhov wrote:
> > There is a demand from driver's writers to use managed devices framework
> > for their drivers. Unfortunately up to this moment input devices did not
> > provide support for managed devices and that lead to mixing two styles
> > of resource management which usually introduced more bugs, such as
> > manually unregistering input device but relying in devres to free
> > interrupt handler which (unless device is properly shut off) can cause
> > ISR to reference already freed memory.
> > 
> > This change introduces devm_input_allocate_device() that will allocate
> > managed instance of input device so that driver writers who prefer
> > using devm_* framework do not have to mix 2 styles.
> 
> It generally looks good to me although it's a bit unusual to use
> devres on device.  Given the way input_dev is used, it probably makes
> sense, I guess.
> 
> One thing tho.  If possible and there aren't too many, wouldn't it be
> better to convert all to use devres.  Having two different lifetime
> fules tends to lead to gotchas.

Not all drivers use devres for rest of their resources so it makes sense
to have unmanaged versions (like we have request_irq/devm_request_irq).
Besides:

[dtor@...r-ws vmci]$ grep -r input_allocate_device drivers/ | wc -l
298

so I'd rather not ;)

Thanks.

-- 
Dmitry

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