linux-kernel - Re: drivers/input/touchscreen/ads7846.c:705:24: warning: taking address of packed member 'data' of class or structure 'ads7846_buf' may result in an unaligned pointer value

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Message-ID: <YfWj+hnMiK8dECOp@dev-arch.archlinux-ax161>
Date:   Sat, 29 Jan 2022 13:30:50 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     kernel test robot <lkp@...el.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: drivers/input/touchscreen/ads7846.c:705:24: warning: taking
 address of packed member 'data' of class or structure 'ads7846_buf' may
 result in an unaligned pointer value

On Sun, Jan 30, 2022 at 12:10:55AM +0800, kernel test robot wrote:
> Hi Dmitry,
> 
> FYI, the error/warning still remains.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   cb323ee75d24e7acc2f188d123ba6df46159cf09
> commit: 415e915fdfc775ad0c6675fde1008f6f43dd6251 Merge tag 'v5.11' into next
> date:   11 months ago
> config: mips-randconfig-r025-20220129 (https://download.01.org/0day-ci/archive/20220130/202201300020.SS6KSznh-lkp@intel.com/config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 33b45ee44b1f32ffdbc995e6fec806271b4b3ba4)
> 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=415e915fdfc775ad0c6675fde1008f6f43dd6251
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 415e915fdfc775ad0c6675fde1008f6f43dd6251
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash arch/mips/kernel/ drivers/input/touchscreen/
> 
> 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/input/touchscreen/ads7846.c:705:24: warning: taking address of packed member 'data' of class or structure 'ads7846_buf' may result in an unaligned pointer value [-Waddress-of-packed-member]
>            value = be16_to_cpup(&buf->data);
>                                  ^~~~~~~~~
>    1 warning generated.

Same root cause as https://lore.kernel.org/r/YenXz+RznXBuJMSR@dev-arch.archlinux-ax161/.

Fixed with https://lore.kernel.org/r/20220125221925.3547683-2-nathan@kernel.org/.

Sorry for the noise, this should have only been sent to our mailing
list, not maintainers.

Cheers,
Nathan