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

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Date:   Sun, 09 Jun 2019 06:35:07 -0700
From:   Joe Perches <joe@...ches.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Julia Lawall <julia.lawall@...6.fr>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Media Mailing List <linux-media@...r.kernel.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 Sun, 2019-06-09 at 22:08 +0900, Masahiro Yamada wrote:
> On Sun, Jun 9, 2019 at 8:57 PM Joe Perches <joe@...ches.com> wrote:
> > On Sun, 2019-06-09 at 16:14 +0900, Masahiro Yamada wrote:
> > > Hi Joe,
> > > 
> > > On Thu, Jun 6, 2019 at 2:06 AM Joe Perches <joe@...ches.com> wrote:
> > > > Perhaps a checkpatch change too:
> > > > 
> > > > The first block updates unsigned only bitfields
> > > > The second tests uapi definitions and suggests "__<kernel_types"
> > > 
> > > Good.
> > > 
> > > In addition,
> > > 
> > > "warn if __u8, __u16, __u32, __u64 are used outside of uapi/"
> > > 
> > > Lots of kernel-space headers use __u{8,16,32,64} instead of u{8,16,32,64}
> > > just because developers often miss to understand when to use
> > > the underscore-prefixed types.
> > 
> > The problem there is that checkpatch can't know if the
> > __<uapi_type> being used is for an actual uapi use or not.
> > 
> > coccinelle could be much better at that.
> 
> Why?


Perhaps it's (somewhat) bad form to have a __uapi type in a
structure, include that structure in a driver for something
like a copy_to/from_user, and map the __<uapi_type> to a non
underscore prefixed <kernel_type>

For instance

struct flat_binder_object in drivers/android/binder.c

How is checkpatch supposed to know that __u32 flags is
inappropriate?