linux-kernel - Re: drivers/iio/adc/ti-tsc2046.c:242:62: warning: taking address of packed member 'data' of class or structure 'tsc2046_adc_atom' may result in an unaligned pointer value

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Message-ID: <20220117101941.00003c68@Huawei.com>
Date:   Mon, 17 Jan 2022 10:19:41 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     kernel test robot <lkp@...el.com>
CC:     Oleksij Rempel <o.rempel@...gutronix.de>, <llvm@...ts.linux.dev>,
        <kbuild-all@...ts.01.org>, <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: drivers/iio/adc/ti-tsc2046.c:242:62: warning: taking address of
 packed member 'data' of class or structure 'tsc2046_adc_atom' may result in
 an unaligned pointer value

On Mon, 17 Jan 2022 18:00:03 +0800
kernel test robot <lkp@...el.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   0c947b893d69231a9add855939da7c66237ab44f
> commit: 9374e8f5a38defe90bc65b2decf317c1c62d91dd iio: adc: add ADC driver for the TI TSC2046 controller
> date:   8 months ago
> config: mips-randconfig-r002-20220116 (https://download.01.org/0day-ci/archive/20220117/202201171718.7ZCI4YeQ-lkp@intel.com/config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project c63a3175c2947e8c1a2d3bbe16a8586600705c54)
> 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=9374e8f5a38defe90bc65b2decf317c1c62d91dd
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 9374e8f5a38defe90bc65b2decf317c1c62d91dd
>         # 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/iio/adc/ drivers/usb/gadget/
> 
> 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/iio/adc/ti-tsc2046.c:242:62: warning: taking address of packed member 'data' of class or structure 'tsc2046_adc_atom' may result in an unaligned pointer value [-Waddress-of-packed-member]  
>            return FIELD_GET(TI_TSC2046_DATA_12BIT, get_unaligned_be16(&buf->data));
>                                                                        ^~~~~~~~~

I'm open to suggestions on what (if anything) to do about this one...

Jonathan

>    include/linux/bitfield.h:108:27: note: expanded from macro 'FIELD_GET'
>                    __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");       \
>                                            ^~~~
>    include/linux/bitfield.h:52:38: note: expanded from macro '__BF_FIELD_CHECK'
>                    BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull,         \
>                                                       ^~~~
>    include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
>    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>                                                             ^~~~
>    include/linux/compiler_types.h:328:22: note: expanded from macro 'compiletime_assert'
>            _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>                                ^~~~~~~~~
>    include/linux/compiler_types.h:316:23: note: expanded from macro '_compiletime_assert'
>            __compiletime_assert(condition, msg, prefix, suffix)
>                                 ^~~~~~~~~
>    include/linux/compiler_types.h:308:9: note: expanded from macro '__compiletime_assert'
>                    if (!(condition))                                       \
>                          ^~~~~~~~~
>    1 warning generated.
> 
> 
> vim +242 drivers/iio/adc/ti-tsc2046.c
> 
>    239	
>    240	static u16 tsc2046_adc_get_value(struct tsc2046_adc_atom *buf)
>    241	{
>  > 242		return FIELD_GET(TI_TSC2046_DATA_12BIT, get_unaligned_be16(&buf->data));  
>    243	}
>    244	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org