Re: [PATCH v2 1/6] iio: introduce IIO_DECLARE_BUFFER_WITH_TS macros

[kernel test robot <lkp@intel.com>]

Hi David,

kernel test robot noticed the following build errors:

[auto build test ERROR on aff301f37e220970c2f301b5c65a8bfedf52058e]

url:    https://github.com/intel-lab-lkp/linux/commits/David-Lechner/iio-introduce-IIO_DECLARE_BUFFER_WITH_TS-macros/20250423-061049
base:   aff301f37e220970c2f301b5c65a8bfedf52058e
patch link:    https://lore.kernel.org/r/20250422-iio-introduce-iio_declare_buffer_with_ts-v2-1-3fd36475c706%40baylibre.com
patch subject: [PATCH v2 1/6] iio: introduce IIO_DECLARE_BUFFER_WITH_TS macros
config: sh-randconfig-001-20250424 (https://download.01.org/0day-ci/archive/20250424/202504240112.hZy9LpvD-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 12.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250424/202504240112.hZy9LpvD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202504240112.hZy9LpvD-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/iio/industrialio-buffer.c:29:
>> include/linux/iio/iio.h:813:1: error: static assertion failed: "macros above assume that IIO_DMA_MINALIGN also ensures s64 timestamp alignment"
     813 | _Static_assert(sizeof(IIO_DMA_MINALIGN) % sizeof(s64) == 0,
         | ^~~~~~~~~~~~~~


vim +813 include/linux/iio/iio.h

   781	
   782	#define _IIO_DECLARE_BUFFER_WITH_TS(type, name, count) \
   783		type name[ALIGN((count), sizeof(s64) / sizeof(type)) + sizeof(s64) / sizeof(type)]
   784	
   785	/**
   786	 * IIO_DECLARE_BUFFER_WITH_TS() - Declare a buffer with timestamp
   787	 * @type: element type of the buffer
   788	 * @name: identifier name of the buffer
   789	 * @count: number of elements in the buffer
   790	 *
   791	 * Declares a buffer that is safe to use with iio_push_to_buffer_with_ts(). In
   792	 * addition to allocating enough space for @count elements of @type, it also
   793	 * allocates space for a s64 timestamp at the end of the buffer and ensures
   794	 * proper alignment of the timestamp.
   795	 */
   796	#define IIO_DECLARE_BUFFER_WITH_TS(type, name, count) \
   797		_IIO_DECLARE_BUFFER_WITH_TS(type, name, count) __aligned(sizeof(s64))
   798	
   799	/**
   800	 * IIO_DECLARE_DMA_BUFFER_WITH_TS() - Declare a DMA-aligned buffer with timestamp
   801	 * @type: element type of the buffer
   802	 * @name: identifier name of the buffer
   803	 * @count: number of elements in the buffer
   804	 *
   805	 * Same as IIO_DECLARE_BUFFER_WITH_TS(), but is uses __aligned(IIO_DMA_MINALIGN)
   806	 * to ensure that the buffer doesn't share cachelines with anything that comes
   807	 * before it in a struct. This should not be used for stack-allocated buffers
   808	 * as stack memory cannot generally be used for DMA.
   809	 */
   810	#define IIO_DECLARE_DMA_BUFFER_WITH_TS(type, name, count) \
   811		_IIO_DECLARE_BUFFER_WITH_TS(type, name, count) __aligned(IIO_DMA_MINALIGN)
   812	
 > 813	_Static_assert(sizeof(IIO_DMA_MINALIGN) % sizeof(s64) == 0,
   814		"macros above assume that IIO_DMA_MINALIGN also ensures s64 timestamp alignment");
   815	

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