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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Sat, 30 Mar 2019 21:52:46 +0900
Message-ID: <CAK7LNATKqbb1L4LzofncJsYCUL1iDwUyy6WOTOE0X82ydVPDdg@mail.gmail.com>
Subject: Re: [PATCH 4/4] CPER: Remove unnecessary use of user-space types
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     linux-pci@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
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On Tue, Mar 26, 2019 at 3:26 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Mon, Mar 25, 2019 at 01:14:25PM -0500, helgaas@kernel.org wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> >
> > "__u32" and similar types are intended for things exported to user-space,
> > including structs used in ioctls; see include/uapi/asm-generic/int-l64.h.
> >
> > They are not needed for the CPER struct definitions, which not exported to
> > user-space and not used in ioctls.  Replace them with the typical "u32" and
> > similar types.  No functional change intended.
> >
> > The reason for changing this is to remove the question of "why do we use
> > __u32 here instead of u32?"  We should use __u32 when there's a reason for
> > it; otherwise, we should prefer u32 for consistency.
> >
> > Reference: Documentation/process/coding-style.rst
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > CC: Masahiro Yamada <yamada.masahiro@socionext.com>
> > CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > CC: Andrew Morton <akpm@linux-foundation.org>
>
> I cc'd you folks because you were part of this conversation:
>
>   https://lore.kernel.org/lkml/1526350925-14922-3-git-send-email-yamada.masahiro@socionext.com/T/#u
>
> I *think* the conclusion there was that this sort of change makes
> sense, but I want to make sure.  If it does make sense, I'm surprised
> at how much stuff in include/linux/ still uses __u32 when it doesn't
> appear to need it.


This patch looks good to me.

I still fail to understand Greg's comment in
the referred URL, though.


"__u32" and similar types are intended for things exported to user-space.

This is clearly documented.

Documentation/process/coding-style.rst:

 (e) Types safe for use in userspace.

     In certain structures which are visible to userspace, we cannot
     require C99 types and cannot use the ``u32`` form above. Thus, we
     use __u32 and similar types in all structures which are shared
     with userspace.


I'd be eager to see a document that suggests __u32 and similar types
in ioctl structures.


--
Best Regards
Masahiro Yamada