Re: [PATCH v2 3/3] of: Respect #{iommu,msi}-cells in maps

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

Hi Vijayanand,

kernel test robot noticed the following build warnings:

[auto build test WARNING on xen-tip/linux-next]
[also build test WARNING on v6.18]
[cannot apply to robh/for-next pci/next pci/for-linus linus/master next-20251204]
[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/Vijayanand-Jitta/of-Add-convenience-wrappers-for-of_map_id/20251204-180719
base:   https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git linux-next
patch link:    https://lore.kernel.org/r/20251204095530.8627-4-vijayanand.jitta%40oss.qualcomm.com
patch subject: [PATCH v2 3/3] of: Respect #{iommu,msi}-cells in maps
config: arm-allnoconfig (https://download.01.org/0day-ci/archive/20251205/202512051152.PJ6mf512-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project d8b43edf552840e59a22a7f3cc332697bd434782)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251205/202512051152.PJ6mf512-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/202512051152.PJ6mf512-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/of/base.c:2144:7: warning: variable 'cells' is used uninitialized whenever '&&' condition is false [-Wsometimes-uninitialized]
    2144 |                 if (!bad_map && of_property_read_u32(phandle_node, cells_name, &cells)) {
         |                     ^~~~~~~~
   drivers/of/base.c:2149:30: note: uninitialized use occurs here
    2149 |                 if (map_len - offset < 3 + cells)
         |                                            ^~~~~
   drivers/of/base.c:2144:7: note: remove the '&&' if its condition is always true
    2144 |                 if (!bad_map && of_property_read_u32(phandle_node, cells_name, &cells)) {
         |                     ^~~~~~~~~~~
   drivers/of/base.c:2125:30: note: initialize the variable 'cells' to silence this warning
    2125 |                 u32 id_base, phandle, cells, id_len, id_off;
         |                                            ^
         |                                             = 0
   1 warning generated.


vim +2144 drivers/of/base.c

  2065	
  2066	/**
  2067	 * of_map_id - Translate an ID through a downstream mapping.
  2068	 * @np: root complex device node.
  2069	 * @id: device ID to map.
  2070	 * @map_name: property name of the map to use.
  2071	 * @cells_name: property name of target specifier cells.
  2072	 * @map_mask_name: optional property name of the mask to use.
  2073	 * @arg: contains the optional params, @target which is a pointer
  2074	 *	to the target device node and id_out which is a pointer
  2075	 *	to receive the translated ID.
  2076	 *
  2077	 * Given a device ID, look up the appropriate implementation-defined
  2078	 * platform ID and/or the target device which receives transactions on that
  2079	 * ID, as per the "iommu-map" and "msi-map" bindings. Either of @target or
  2080	 * @id_out may be NULL if only the other is required. If @target points to
  2081	 * a non-NULL device node pointer, only entries targeting that node will be
  2082	 * matched; if it points to a NULL value, it will receive the device node of
  2083	 * the first matching target phandle, with a reference held.
  2084	 *
  2085	 * Return: 0 on success or a standard error code on failure.
  2086	 */
  2087	int of_map_id(const struct device_node *np, u32 id, const char *map_name,
  2088		      const char *cells_name, const char *map_mask_name,
  2089		      struct of_map_id_arg *arg)
  2090	{
  2091		u32 map_mask, masked_id;
  2092		int map_bytes, map_len, offset = 0;
  2093		bool bad_map = false;
  2094		const __be32 *map = NULL;
  2095	
  2096		if (!np || !map_name || !arg || (!arg->target && !arg->id_out))
  2097			return -EINVAL;
  2098	
  2099		map = of_get_property(np, map_name, &map_bytes);
  2100		if (!map) {
  2101			if (arg->target)
  2102				return -ENODEV;
  2103			/* Otherwise, no map implies no translation */
  2104			*arg->id_out = id;
  2105			return 0;
  2106		}
  2107	
  2108		if (map_bytes % sizeof(*map))
  2109			goto err_map_len;
  2110		map_len = map_bytes / sizeof(*map);
  2111	
  2112		/* The default is to select all bits. */
  2113		map_mask = 0xffffffff;
  2114	
  2115		/*
  2116		 * Can be overridden by "{iommu,msi}-map-mask" property.
  2117		 * If of_property_read_u32() fails, the default is used.
  2118		 */
  2119		if (map_mask_name)
  2120			of_property_read_u32(np, map_mask_name, &map_mask);
  2121	
  2122		masked_id = map_mask & id;
  2123		while (offset < map_len) {
  2124			struct device_node *phandle_node;
  2125			u32 id_base, phandle, cells, id_len, id_off;
  2126			const __be32 *out_base;
  2127	
  2128			if (map_len - offset < 2)
  2129				goto err_map_len;
  2130	
  2131			id_base = be32_to_cpup(map + offset);
  2132			if (id_base & ~map_mask) {
  2133				pr_err("%pOF: Invalid %s translation - %s (0x%x) ignores id-base (0x%x)\n",
  2134					np, map_name, map_mask_name,
  2135					map_mask, id_base);
  2136				return -EFAULT;
  2137			}
  2138	
  2139			phandle = be32_to_cpup(map + offset + 1);
  2140			phandle_node = of_find_node_by_phandle(phandle);
  2141			if (!phandle_node)
  2142				return -ENODEV;
  2143	
> 2144			if (!bad_map && of_property_read_u32(phandle_node, cells_name, &cells)) {

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