linux-kernel - Re: [PATCH] mtd: onenand_base: Avoid fall-through warnings

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Message-ID: <201905221444.014568B0F4@keescook>
Date:   Wed, 22 May 2019 14:45:15 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: onenand_base: Avoid fall-through warnings

On Wed, May 22, 2019 at 11:37:05PM +0200, Boris Brezillon wrote:
> > @@ -3280,12 +3280,14 @@ static void onenand_check_features(struct mtd_info *mtd)
> >  			if ((this->version_id & 0xf) == 0xe)
> >  				this->options |= ONENAND_HAS_NOP_1;
> >  		}
> > +		/* Fall through - ? */
> 
> So, the only thing that you'll re-use by falling through the next case
> is the '->options |= ONENAND_HAS_UNLOCK_ALL' operation. I find it easier
> to follow with an explicit copy of this line + a break.
> 
> >  
> >  	case ONENAND_DEVICE_DENSITY_2Gb:
> >  		/* 2Gb DDP does not have 2 plane */
> >  		if (!ONENAND_IS_DDP(this))
> >  			this->options |= ONENAND_HAS_2PLANE;
> >  		this->options |= ONENAND_HAS_UNLOCK_ALL;
> > +		/* Fall through - ? */
> 
> This fall through certainly doesn't make sense, as the only thing that
> might be done in the 1Gb case is conditionally adding the
> HAS_UNLOCK_ALL flag, and this flag is already unconditionally set.
> Please add a break here.
> 
> >  
> >  	case ONENAND_DEVICE_DENSITY_1Gb:
> >  		/* A-Die has all block unlock */
> 

Your reply was much more to-the-point than mine. :) I'd agree: retain
existing behavior (ONENAND_HAS_UNLOCK_ALL) and add breaks.

-- 
Kees Cook