linux-kernel - Re: [PATCH] media: do not use C++ style comments in uapi headers

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Message-ID: <CAK7LNAQYOXZTUiQH1opbh3duipvLtQZvwb10STUj4YHZdTfM_A@mail.gmail.com>
Date:   Wed, 5 Jun 2019 19:08:35 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Joe Perches <joe@...ches.com>, Arnd Bergmann <arnd@...db.de>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: do not use C++ style comments in uapi headers

On Wed, Jun 5, 2019 at 3:03 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Tue, Jun 04, 2019 at 10:22:05PM -0700, Joe Perches wrote:
> > On Wed, 2019-06-05 at 07:10 +0200, Greg KH wrote:
> > > On Wed, Jun 05, 2019 at 01:10:41PM +0900, Masahiro Yamada wrote:
> > > > On Wed, Jun 5, 2019 at 3:21 AM Arnd Bergmann <arnd@...db.de> wrote:
> > []
> > > > This means we cannot reliably use uint{8,16,32,64}_t in UAPI headers.
> > >
> > > We should not be doing that as they are in the userspace "namespace" of
> > > variables, not in the kernel namespace.  We've been over this many times
> > > in the past :(
> >
> > Just not very successfully...
> >
> > $ git grep -w -P 'u?_?int(?:8|16|32|64)_t' include/uapi | wc -l
> > 342
> >
> > $ git grep -w -P --name-only 'u?_?int(?:8|16|32|64)_t' include/uapi | wc -l
> > 13
> >
> > Documentation helps a bit, checkpatch helps as well.
> > Maintainer knowledge and vigilance probably helps the most.
>
> Yes, it's not been a dedicated effort at all :(


I am proposing this series.
https://lkml.org/lkml/2019/6/4/1379


When CONFIG_UAPI_HEADER_TEST=y,
UAPI headers are compile-tested.

0-day bot tests allmodconfig, which enables CONFIG_UAPI_HEADER_TEST,
so new buggy headers will be blocked.

It will take some time to eliminate existing bugs.
I just started with low-hanging fruits:

https://lore.kernel.org/patchwork/patch/1083711/
https://lore.kernel.org/patchwork/patch/1084123/



Anyway, having a document will be really nice.

Not all maintainers understand the detail.
Having some evidence in Documentation/
will help the review process move smoothly.


> But it needs to be resolved, if we want people to actually use our
> kernel headers easily.
>
> thanks,
>
> greg k-h



-- 
Best Regards
Masahiro Yamada