Re: [PATCH 5/6] of: add infra to parse iommu-map per IOMMU cell count

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

Hi Charan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on robh/for-next]
[also build test WARNING on linus/master v6.18-rc4 next-20251103]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Charan-Teja-Kalla/of-create-a-wrapper-for-of_map_id/20251104-170223
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/74d4ddf90c0fb485fda1feec5116dc38e5fd23cf.1762235099.git.charan.kalla%40oss.qualcomm.com
patch subject: [PATCH 5/6] of: add infra to parse iommu-map per IOMMU cell count
config: loongarch-allnoconfig (https://download.01.org/0day-ci/archive/20251104/202511041853.IxYgvWlc-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project d2625a438020ad35330cda29c3def102c1687b1b)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251104/202511041853.IxYgvWlc-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/202511041853.IxYgvWlc-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/of/base.c:2127:6: warning: variable 'legacy_iommu_cells' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    2127 |         if (map_len % 4 != 0)
         |             ^~~~~~~~~~~~~~~~
   drivers/of/base.c:2130:9: note: uninitialized use occurs here
    2130 |         return legacy_iommu_cells ? : of_iommu_map_id_actual_cell_count(map, map_len, cells);
         |                ^~~~~~~~~~~~~~~~~~
   drivers/of/base.c:2127:2: note: remove the 'if' if its condition is always true
    2127 |         if (map_len % 4 != 0)
         |         ^~~~~~~~~~~~~~~~~~~~~
    2128 |                 legacy_iommu_cells = of_iommu_map_id_legacy_cell_count(map, map_len);
   drivers/of/base.c:2125:24: note: initialize the variable 'legacy_iommu_cells' to silence this warning
    2125 |         u32 legacy_iommu_cells;
         |                               ^
         |                                = 0
   1 warning generated.


vim +2127 drivers/of/base.c

c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2110  
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2111  /**
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2112   * of_iommu_map_id_cell_count - Determine the cell count for iommu-map parsing.
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2113   *
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2114   * @map: pointer to the iommu-map property that needs to be translated.
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2115   * @map_len: length of @map in bytes.
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2116   *
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2117   * Use #iommu-cells property while parsing iommu-map. Detect and use legacy
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2118   * case where iommu-map is parsed as if cells = 1.
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2119   *
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2120   * Return: number of cells that the caller should be considered while parsing
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2121   * the @map. It is > 0 for success, 0 for failure.
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2122   */
5288ad2aeeeb41 Charan Teja Kalla 2025-11-04  2123  static int of_iommu_map_id_cell_count(const __be32 *map, int map_len, u32 cells)
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2124  {
5288ad2aeeeb41 Charan Teja Kalla 2025-11-04  2125  	u32 legacy_iommu_cells;
5288ad2aeeeb41 Charan Teja Kalla 2025-11-04  2126  
c74d6f4acf99ef Charan Teja Kalla 2025-11-04 @2127  	if (map_len % 4 != 0)
5288ad2aeeeb41 Charan Teja Kalla 2025-11-04  2128  		legacy_iommu_cells = of_iommu_map_id_legacy_cell_count(map, map_len);
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2129  
5288ad2aeeeb41 Charan Teja Kalla 2025-11-04  2130  	return legacy_iommu_cells ? : of_iommu_map_id_actual_cell_count(map, map_len, cells);
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2131  }
c74d6f4acf99ef Charan Teja Kalla 2025-11-04  2132  

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