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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sun, 21 Jul 2019 16:15:05 +0200
Message-ID: <CAK8P3a133ekPqkLWfC2ee0mT3iLbFzSjJ9FDokSyaX+hMVigKA@mail.gmail.com>
Subject: Re: [Question] orphan platform data header
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     Ben Dooks <ben.dooks@codethink.co.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        DTML <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
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On Sun, Jul 21, 2019 at 2:13 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> On Sun, Jul 21, 2019 at 6:10 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > On Sun, Jul 21, 2019 at 5:45 AM Masahiro Yamada
> > <yamada.masahiro@socionext.com> wrote:
> > > On Sat, Jul 20, 2019 at 10:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > > > On Sat, Jul 20, 2019 at 5:26 AM Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>
>
> Another example that I have no idea
> how it works:
>
> drivers/net/hamradio/yam.c
>
> yam_ioctl() reads data from user-space,
> but the data structures for ioctl are
> defined in include/linux/yam.h

That is different: the hardware attaches to a serial port and may well
be usable, and the user space side just contains a copy of the header,
see https://github.com/nwdigitalradio/ax25-tools/tree/master/yamdrv

> If we want to fix this, we could move it
> to include/uapi/linux/yam.h

We could do that, or just leave it alone, as nobody would
tell the difference.

> But, if nobody has reported any problem about this,
> it might be a good proof that nobody is using this driver.
>
> Maybe, can we simply drop odd drivers??

Both the kernel driver and the user space side have a maintainer, and
I see no indication that it is actually broken. The driver is clearly
a relic from old times (earlier than 2.4) and we would not merge
this driver today.

It seems more useful to keep looking for drivers with a platform_data
header file that is no longer included by any platform for candidates
that may be obsolete.

        Arnd