Hi "Christian,

I love your patch! Perhaps something to improve:

[auto build test WARNING on drm-intel/for-linux-next]
[also build test WARNING on drm-exynos/exynos-drm-next tegra-drm/drm/tegra/for-next linus/master v5.13-rc6 next-20210616]
[cannot apply to drm-tip/drm-tip drm/drm-next]
[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]

url:    https://github.com/0day-ci/linux/commits/Christian-K-nig/dma-buf-some-dma_fence_chain-improvements/20210616-182806
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: alpha-randconfig-s031-20210615 (attached as .config)
compiler: alpha-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-341-g8af24329-dirty
        # https://github.com/0day-ci/linux/commit/058b99a2929f84c7f2cb1516dcc8674bf3f2a661
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Christian-K-nig/dma-buf-some-dma_fence_chain-improvements/20210616-182806
        git checkout 058b99a2929f84c7f2cb1516dcc8674bf3f2a661
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=alpha 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)
>> drivers/dma-buf/dma-fence-chain.c:28:15: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected struct dma_fence_chain **_x_ @@     got struct dma_fence_chain [noderef] __rcu ** @@
   drivers/dma-buf/dma-fence-chain.c:28:15: sparse:     expected struct dma_fence_chain **_x_
   drivers/dma-buf/dma-fence-chain.c:28:15: sparse:     got struct dma_fence_chain [noderef] __rcu **
>> drivers/dma-buf/dma-fence-chain.c:28:13: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected struct dma_fence_chain [noderef] __rcu **tmp @@     got struct dma_fence_chain **[assigned] __ret @@
   drivers/dma-buf/dma-fence-chain.c:28:13: sparse:     expected struct dma_fence_chain [noderef] __rcu **tmp
   drivers/dma-buf/dma-fence-chain.c:28:13: sparse:     got struct dma_fence_chain **[assigned] __ret

vim +28 drivers/dma-buf/dma-fence-chain.c

    16	
    17	/**
    18	 * dma_fence_chain_enqueue - enqeue a chain node for garbage collection
    19	 * @chain: the chain node to enqueue
    20	 *
    21	 * Add the chain node to the end of the gc fifo.
    22	 */
    23	static void dma_fence_chain_enqueue(struct dma_fence_chain *chain)
    24	{
    25		struct dma_fence_chain __rcu **tmp;
    26	
    27		RCU_INIT_POINTER(chain->next, NULL);
  > 28		tmp = xchg((struct dma_fence_chain __force ***)&fifo_back,
    29			   &chain->next);
    30	
    31		/* This is intentionally unordered since we only need the fifo for gc */
    32		rcu_assign_pointer(*tmp, chain);
    33	}
    34	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org