linux-kernel - 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: <202112261050.OodYJnM4-lkp@intel.com>
Date:   Sun, 26 Dec 2021 10:58:54 +0800
From:   kernel test robot <lkp@...el.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: 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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   e2ae0d4a6b0ba461542f0fd0ba0b828658013e9f
commit: 415e915fdfc775ad0c6675fde1008f6f43dd6251 Merge tag 'v5.11' into next
date:   10 months ago
config: mips-randconfig-r033-20211226 (https://download.01.org/0day-ci/archive/20211226/202112261050.OodYJnM4-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 0c553cc1af2e4c14100df6cf4a6fc91987e778e6)
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 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.


vim +705 drivers/input/touchscreen/ads7846.c

2991a1ca6e9b13 Jason Wang     2010-10-13  700  
6965eece2a89c3 Oleksij Rempel 2021-01-20  701  static int ads7846_get_value(struct ads7846_buf *buf)
2991a1ca6e9b13 Jason Wang     2010-10-13  702  {
879f2fea8a5a74 Andrey Gelman  2015-10-06  703  	int value;
2991a1ca6e9b13 Jason Wang     2010-10-13  704  
6965eece2a89c3 Oleksij Rempel 2021-01-20 @705  	value = be16_to_cpup(&buf->data);
879f2fea8a5a74 Andrey Gelman  2015-10-06  706  
879f2fea8a5a74 Andrey Gelman  2015-10-06  707  	/* enforce ADC output is 12 bits width */
879f2fea8a5a74 Andrey Gelman  2015-10-06  708  	return (value >> 3) & 0xfff;
2991a1ca6e9b13 Jason Wang     2010-10-13  709  }
ffa458c1bd9b6f David Brownell 2006-01-08  710  

:::::: The code at line 705 was first introduced by commit
:::::: 6965eece2a89c3f1d00881c6052ee1e987870c08 Input: ads7846 - convert to one message

:::::: TO: Oleksij Rempel <o.rempel@...gutronix.de>
:::::: CC: Dmitry Torokhov <dmitry.torokhov@...il.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org