linux-kernel - Re: [PATCH 1/2] drivers: usb: gadget: udc: add missing break in switch

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Date:   Wed, 8 Feb 2017 14:03:57 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        bhumirks@...il.com, mina86@...a86.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drivers: usb: gadget: udc: add missing break in
 switch

On Wed, Feb 08, 2017 at 02:05:35PM +0200, Felipe Balbi wrote:
> 
> Hi,
> 
> "Gustavo A. R. Silva" <garsilva@...eddedor.com> writes:
> >> "Gustavo A. R. Silva" <garsilva@...eddedor.com> writes:
> >>> Add missing break in switch.
> >>>
> >>> Addresses-Coverity-ID: 201385
> >>> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> >>> ---
> >>>  drivers/usb/gadget/udc/mv_udc_core.c | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/drivers/usb/gadget/udc/mv_udc_core.c  
> >>> b/drivers/usb/gadget/udc/mv_udc_core.c
> >>> index 27ebb0d..56b3574 100644
> >>> --- a/drivers/usb/gadget/udc/mv_udc_core.c
> >>> +++ b/drivers/usb/gadget/udc/mv_udc_core.c
> >>> @@ -489,6 +489,7 @@ static int mv_ep_enable(struct usb_ep *_ep,
> >>>  		break;
> >>>  	case USB_ENDPOINT_XFER_CONTROL:
> >>>  		ios = 1;
> >>> +		break;
> >>
> >> are you SURE this is supposed to have this break statement? What if we
> >> want to initialize mult to 0 *also* for control endpoints? How did you
> >> test this? Do you have access to Marvel's documentation for this
> >> controller?
> >>
> >
> > Certainly I wasn't sure, but I also think this is kind of obscure  
> > code. If that is the case that we also want to initialize mult to 0,  
> > wouldn't it be clearer (for maintenance purposes) to add mult = 0 and  
> > the break statement after ios = 1?
> >
> > What do you think if I modify that piece of code as follows:
> 
> I think you need to test it, or get someone to test it for you :-)

For crap code like this where it's "obvious" that something is wrong?
That's really hard.

How about a nice comment instead:
	/* Code path falls through, is it correct or not, who knows??? */
which will make the static code checkers stop complaining about it, and
if someone actually has the hardware, then they can test it.

thanks,

greg k-h