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SubjectRe: [PATCH 25/25] leds: convert One-shot LED trigger driver to devm_kzalloc() and cleanup error exit path
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On Thu, 2012-07-05 at 21:48 +0200, Fabio Baltieri wrote:

> > >
> > Bryan,
> >
> > I don't believe memory triggers allocate in their activate routine
> > should be converted to devm_kzalloc(). Based on my understanding, the
> > memory allocated using devm_kzalloc() us free'ed when driver is
> > detached. In the case of led triggers, driver stays registered while the
> > triggers it supports can be activated and deactivated many times. By
> > converting these allocations into devm_kzalloc()s could lead to memory
> > leaks. Please correct me if my understanding is incorrect.
>
> Shuah,
>
> I'm as the same opinion - as triggers are not really "driver", in the
> sense that they are not using the driver structures, using devm_
> functions doesn't seems to be really appropriate.
>

Correct. Each driver could support multiple triggers and triggers are
not at the same level as the device.

> Specifically:
>
> > > + oneshot_data = devm_kzalloc(led_cdev->dev, sizeof(*oneshot_data),
> > > + GFP_KERNEL);
>
> this one is registering the data on the relative LED's resources, so
> that they are not freed until you unload the LED's driver itself.
> I also think that this leads to memory leak if you keep activating
> triggers, as the deactivate function is not actually freeing the
> resources, so in that case the correct procedure should be the usual
> kalloc/kfree.
>
> Is this consistent with what your conclusions, Shuah?

Correct. Using devm_ in triggers is not the correct and there is no need
to change from using kalloc()/kfree().

-- Shuah
>
> Fabio
>
> > If what I am saying makes sense, please take this as comment that is
> > applicable to all led triggers, not just this one.
> >
> > Thanks,
> > -- Shuah
> >
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