Re: [PATCH] fujitsu-laptop: driver [un]registration fixes

Dmitry Torokhov
2009-12-21T22:46:50Z

Hi Jonathan,

On Monday 21 December 2009 02:32:40 pm Jonathan Woithe wrote:
> Hi Dmitry
>
> > On Wed, Jul 29, 2009 at 10:15:33PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > > @@ -722,22 +722,22 @@ static int acpi_fujitsu_add(struct acpi_
> > >
> > > return result;
> > >
> > > -end:
> > > +err_unregister_input_dev:
> > > + input_unregister_device(input);
> > > err_free_input_dev:
> > > input_free_device(input);
> > > err_stop:
> >
> > Just noticed it scanning ACPI list. You must not use input_free_device()
> > after calling input_unregister_device() since unregister likely drops the
> > last reference to the device and it will get freed by input core.
>
> So what's the correct way to deal with that in this case? Something like
>
> -end:
> +err_unregister_input_dev:
> + input_unregister_device(input);
> + goto err_stop;
> err_free_input_dev:
> input_free_device(input);
> err_stop:
>
> (with a short comment to explain the goto) would circumvent the problem but
> it looks ugly (at least to my eyes - I've never really liked "goto"s :-) ).

Just do "input = NULL;" after calling input_unregister_device() -
input_free_device() is like kfree() and will happily ignore passed NULL
pointers.

Or rearrange the code to register device last, when everything is ready.

>
> > For polled input devices you need to use both unregister and free though
> > because polled device structure is not refcounted (but underlying input
> > device is).
>
> This isn't a polled input device AFAIK so this doesn't apply here, right?

Right, it was more of a general statement so I don't get bunch of patches
removing input_free_polled_device() after calls to
input_unregister_polled_device() ;)

--
Dmitry