include/linux/bitops.h:279:19: sparse: sparse: cast truncates bits from constant value (ffffffff000 becomes fffff000)

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

tree:   https://github.com/intel-lab-lkp/linux/commits/Daniel-Drake-via-B4-Relay/iommu_pt-Fix-test_pgsize_boundary-failure-on-narrow-OA-formats/20260927-140900
head:   b7ecf4c7cbd115e08bbd71e2959ce77385075e36
commit: 2f4cbf2903187f8af69f9521be028ce204cdd222 iommu/generic_pt: Add Broadcom BCM2712 page table format
date:   4 days ago
config: powerpc-randconfig-r2308-20261001 (https://download.01.org/0day-ci/archive/20261001/202610010359.GypSyCtW-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 8.5.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261001/202610010359.GypSyCtW-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/202610010359.GypSyCtW-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   drivers/iommu/generic_pt/fmt/iommu_bcm2712.c: note: in included file (through include/linux/log2.h, include/asm-generic/div64.h, arch/powerpc/include/generated/asm/div64.h, include/linux/math.h, ...):
>> include/linux/bitops.h:279:19: sparse: sparse: cast truncates bits from constant value (ffffffff000 becomes fffff000)
   include/linux/bitops.h:284:37: sparse: sparse: cast truncates bits from constant value (ffffffff000 becomes fffff000)
>> include/linux/bitops.h:279:19: sparse: sparse: cast truncates bits from constant value (ffffffff000 becomes fffff000)
   include/linux/bitops.h:284:37: sparse: sparse: cast truncates bits from constant value (ffffffff000 becomes fffff000)

vim +279 include/linux/bitops.h

c320592f3f2a1e Wolfram Sang       2025-01-07  267  
952043ac12a117 Steven Whitehouse  2009-04-23  268  /**
952043ac12a117 Steven Whitehouse  2009-04-23  269   * __ffs64 - find first set bit in a 64 bit word
952043ac12a117 Steven Whitehouse  2009-04-23  270   * @word: The 64 bit word
952043ac12a117 Steven Whitehouse  2009-04-23  271   *
4945cca232ce8b Geert Uytterhoeven 2021-02-25  272   * On 64 bit arches this is a synonym for __ffs
952043ac12a117 Steven Whitehouse  2009-04-23  273   * The result is not defined if no bits are set, so check that @word
952043ac12a117 Steven Whitehouse  2009-04-23  274   * is non-zero before calling this.
952043ac12a117 Steven Whitehouse  2009-04-23  275   */
6606c8c7e81886 Kees Cook          2025-08-04  276  static inline __attribute_const__ unsigned int __ffs64(u64 word)
952043ac12a117 Steven Whitehouse  2009-04-23  277  {
952043ac12a117 Steven Whitehouse  2009-04-23  278  #if BITS_PER_LONG == 32
952043ac12a117 Steven Whitehouse  2009-04-23 @279  	if (((u32)word) == 0UL)
952043ac12a117 Steven Whitehouse  2009-04-23  280  		return __ffs((u32)(word >> 32)) + 32;
952043ac12a117 Steven Whitehouse  2009-04-23  281  #elif BITS_PER_LONG != 64
952043ac12a117 Steven Whitehouse  2009-04-23  282  #error BITS_PER_LONG not 32 or 64
952043ac12a117 Steven Whitehouse  2009-04-23  283  #endif
952043ac12a117 Steven Whitehouse  2009-04-23  284  	return __ffs((unsigned long)word);
952043ac12a117 Steven Whitehouse  2009-04-23  285  }
952043ac12a117 Steven Whitehouse  2009-04-23  286  

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