linux-kernel - Re: [PATCH] usb: host: fhci-hcd: annotate PIPE

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Date:   Mon, 17 Feb 2020 15:12:21 +0100
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Timur Tabi <timur@...nel.org>, Li Yang <leoyang.li@....com>,
        Anton Vorontsov <avorontsov@...mvista.com>,
        kbuild test robot <lkp@...el.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] usb: host: fhci-hcd: annotate PIPE_CONTROL switch case
 with fallthrough

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

Rasmus