Re: [PATCH] usb: host: fhci-hcd: annotate PIPE_CONTROL switch case with fallthrough

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Timur Tabi <timur@kernel.org>, Li Yang <leoyang.li@nxp.com>,
	Anton Vorontsov <avorontsov@ru.mvista.com>,
	kbuild test robot <lkp@intel.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	Joe Perches <joe@perches.com>
Subject: Re: [PATCH] usb: host: fhci-hcd: annotate PIPE_CONTROL switch case with fallthrough
Date: Mon, 17 Feb 2020 10:15:09 -0600	[thread overview]
Message-ID: <298629e3-40bb-9530-8292-7e2a9432cd4a@embeddedor.com> (raw)
In-Reply-To: <20200217141831.GA1123892@kroah.com>

Hi!

Sorry for the late reply. I wasn't aware of this thread until now.

Please, see my comments below...

On 2/17/20 08:18, Greg Kroah-Hartman wrote:
> On Mon, Feb 17, 2020 at 03:12:21PM +0100, Rasmus Villemoes wrote:
>> On 17/02/2020 10.38, Greg Kroah-Hartman wrote:
>>> On Thu, Feb 13, 2020 at 02:35:18PM +0100, Rasmus Villemoes wrote:
>>>> On 13/02/2020 13.56, Greg Kroah-Hartman wrote:
>>>>
>>>>> Shouldn't this be /* fall through */ instead?
>>>>>
>>>>> Gustavo, what's the best practice here, I count only a few
>>>>> "fallthrough;" instances in the kernel, although one is in our coding
>>>>> style document, and thousands of the /* */ version.
>>>>
>>>> Yes, I went with the attribute/macro due to that, and the history is
>>>> that Linus applied Joe's patches directly
>>>> (https://lore.kernel.org/lkml/CAHk-=whOF8heTGz5tfzYUBp_UQQzSWNJ_50M7-ECXkfFRDQWFA@mail.gmail.com/),
>>>> so I assumed that meant the Penguin decided that the attribute/macro is
>>>> the right thing to do for new code, while existing comment annotations
>>>> can be left alone or changed piecemeal as code gets refactored anyway.
>>>
>>> But, to be fair, Gustavo went and fixed up thousands of these, with the
>>> /* */ version, not the attribute.
>>>
>>> Gustavo, can coverity notice the "fallthrough;" attribute properly?  I
>>> don't want to start adding things that end up triggering
>>> false-positives.
>>
>> I'm not Gustavo, and I don't know the answer, but 1.5 years ago some guy
>> named greg k-h suggested that coverity does grok the fallthrough attribute:
>>
>> https://patchwork.kernel.org/cover/10651357/#22279095
> 
> I wouldn't trust anything that bum says :)
> 
> Ok, I don't remember saying that at all, but I'll wait a day or two to
> get Gustavo's opinion befor applying the patch.
> 

We are good to go with the 'fallthrough' pseudo keyword. Linus is OK with
that.

The comment annotations will eventually be transformed to "fallthrough;"

Thanks
--
Gustavo