linux-kernel - Re: [PATCH] platform/x86: sony-laptop: Mark expected switch fall-through

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Message-ID: <20180911225121.GE5659@wrath>
Date:   Tue, 11 Sep 2018 15:51:21 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Mattia Dongili <malattia@...ux.it>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: sony-laptop: Mark expected switch
 fall-through

On Sun, Jul 08, 2018 at 03:56:17AM +0900, Mattia Dongili wrote:
> On Fri, Jul 06, 2018 at 04:24:27PM -0700, Darren Hart wrote:
> > On Thu, Jul 05, 2018 at 03:47:03PM -0500, Gustavo A. R. Silva wrote:
> > > In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> > > where we are expecting to fall through.
> > > 
> > > Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> > > ---
> > >  drivers/platform/x86/sony-laptop.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/platform/x86/sony-laptop.c b/drivers/platform/x86/sony-laptop.c
> > > index b205b03..e614cb7 100644
> > > --- a/drivers/platform/x86/sony-laptop.c
> > > +++ b/drivers/platform/x86/sony-laptop.c
> > > @@ -4427,6 +4427,7 @@ sony_pic_read_possible_resource(struct acpi_resource *resource, void *context)
> > >  	default:
> > >  		dprintk("Resource %d isn't an IRQ nor an IO port\n",
> > >  			resource->type);
> > > +		/* fall through */
> > 
> > Here too, I wonder if this is intentional. Either way, from what I can see, the
> > final line in the function:
> > 
> > 	return AE_CTRL_TERMINATE;
> > 
> > Is unreachable as there are no "break" statements in the switch, and the default
> > falls through to return AE_OK. Something doesn't seem right here.
> 
> I think so too. Looks to me that the default case was meant to return
> AE_CTRL_TERMINATE (i.e. swapping it to be last would do).
> 
> Having written that code aeons ago, I'm not sure if there is a good
> reason to be like that, though it still looks like a bug (that
> existed ever since...).
> 
> Want to fix it as part of this patch series? Or I can send a patch
> myself, let me know.

Mattia,

I'd prefer to decouple the fix from the implicit fall through discussion. Please
send a separate fix.

-- 
Darren Hart
VMware Open Source Technology Center