[openeuler:openEuler-1.0-LTS 1528/1528] include/asm-generic/io.h:742:19: warning: 'reg' may be used uninitialized in this function

28 Mar 2025

      tree:   https://gitee.com/openeuler/kernel.git openEuler-1.0-LTS
head:   4d1e247486ffeef035a5a55a97f2659f68177357
commit: e44716ed4262a467260fccb7814e4c89588f438d [1528/1528] arm64: asm-bug: Add .align 2 to the end of __BUG_ENTRY
config: arm64-randconfig-003-20250328 (https://download.01.org/0day-ci/archive/20250328/202503281620.pNXaYE13-lkp@i...)
compiler: aarch64-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250328/202503281620.pNXaYE13-lkp@i...)

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/202503281620.pNXaYE13-lkp@intel.com/

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c: In function 'nv40_fifo_dma_engine_init':
   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:111:37: warning: 'ctx' may be used uninitialized in this function [-Wmaybe-uninitialized]
     111 |  nvkm_wo32(imem->ramfc, chan->ramfc + ctx, inst);
         |                                     ^
   In file included from arch/arm64/include/asm/io.h:213,
                    from include/linux/io.h:25,
                    from include/linux/pci.h:34,
                    from drivers/gpu/drm/nouveau/include/nvif/os.h:8,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/os.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/oclass.h:3,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/device.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/engine.h:5,
                    from drivers/gpu/drm/nouveau/include/nvkm/engine/fifo.h:4,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/priv.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/chan.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/channv04.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:24:
...
...
include/asm-generic/io.h:742:19: warning: 'reg' may be used uninitialized in this function [-Wmaybe-uninitialized]
     742 | #define iowrite32 iowrite32
         |                   ^~~~~~~~~
   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:97:12: note: 'reg' was declared here
      97 |  u32 inst, reg, ctx;
         |            ^~~
   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c: In function 'nv40_fifo_dma_engine_fini':
   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:80:37: warning: 'ctx' may be used uninitialized in this function [-Wmaybe-uninitialized]
      80 |  nvkm_wo32(imem->ramfc, chan->ramfc + ctx, 0x00000000);
         |                                     ^
   In file included from arch/arm64/include/asm/io.h:213,
                    from include/linux/io.h:25,
                    from include/linux/pci.h:34,
                    from drivers/gpu/drm/nouveau/include/nvif/os.h:8,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/os.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/oclass.h:3,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/device.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h:4,
                    from drivers/gpu/drm/nouveau/include/nvkm/core/engine.h:5,
                    from drivers/gpu/drm/nouveau/include/nvkm/engine/fifo.h:4,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/priv.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/chan.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/channv04.h:5,
                    from drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:24:
include/asm-generic/io.h:742:19: warning: 'reg' may be used uninitialized in this function [-Wmaybe-uninitialized]
     742 | #define iowrite32 iowrite32
         |                   ^~~~~~~~~
   drivers/gpu/drm/nouveau/nvkm/engine/fifo/dmanv40.c:67:6: note: 'reg' was declared here
      67 |  u32 reg, ctx;
         |      ^~~
vim +/reg +742 include/asm-generic/io.h

9216efafc52ff9 Thierry Reding 2014-10-01  740  
9216efafc52ff9 Thierry Reding 2014-10-01  741  #ifndef iowrite32
9216efafc52ff9 Thierry Reding 2014-10-01 @742  #define iowrite32 iowrite32
9216efafc52ff9 Thierry Reding 2014-10-01  743  static inline void iowrite32(u32 value, volatile void __iomem *addr)
9216efafc52ff9 Thierry Reding 2014-10-01  744  {
9216efafc52ff9 Thierry Reding 2014-10-01  745  	writel(value, addr);
9216efafc52ff9 Thierry Reding 2014-10-01  746  }
9216efafc52ff9 Thierry Reding 2014-10-01  747  #endif
9216efafc52ff9 Thierry Reding 2014-10-01  748  

:::::: The code at line 742 was first introduced by commit
:::::: 9216efafc52ff99e9351ef60de5fcafc2bc8adb6 asm-generic/io.h: Reconcile I/O accessor overrides

:::::: TO: Thierry Reding <treding@nvidia.com>
:::::: CC: Thierry Reding <treding@nvidia.com>

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