linux-kernel - Re: drivers/media/v4l2-core/v4l2-ioctl.c:303:28: warning: taking address of packed member 'pixelformat' of class or structure 'v4l2_pix_format_mplane' may result in an unaligned pointer value

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Date:   Fri, 5 Nov 2021 12:21:48 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Petr Mladek <pmladek@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: drivers/media/v4l2-core/v4l2-ioctl.c:303:28: warning: taking
 address of packed member 'pixelformat' of class or structure
 'v4l2_pix_format_mplane' may result in an unaligned pointer value

On Fri, Nov 5, 2021 at 12:24 AM kernel test robot <lkp@...el.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   c1e2e0350ce37f633b5ce3ce1cdf4428513fc2a2
> commit: e927e1e0f0dd3e353d5556503a71484008692c82 v4l: ioctl: Use %p4cc printk modifier to print FourCC codes
> date:   9 months ago
> config: mips-randconfig-r011-20211101 (attached as .config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 82ed106567063ea269c6d5669278b733e173a42f)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install mips cross compiling tool for clang build
>         # apt-get install binutils-mips-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e927e1e0f0dd3e353d5556503a71484008692c82
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout e927e1e0f0dd3e353d5556503a71484008692c82
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=mips
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> >> drivers/media/v4l2-core/v4l2-ioctl.c:303:28: warning: taking address of packed member 'pixelformat' of class or structure 'v4l2_pix_format_mplane' may result in an unaligned pointer value [-Waddress-of-packed-member]

Yeah, I discussed it with Sakari a few months ago. Dunno what is the outcome.
TL;DR: some are easy to fix, i.e. by dropping __packed, the rest needs
more thinking...


-- 
With Best Regards,
Andy Shevchenko