Hi Thomas,

I love your patch! Perhaps something to improve:

[auto build test WARNING on next-20200914]
[also build test WARNING on v5.9-rc5]
[cannot apply to linuxtv-media/master drm-intel/for-linux-next tegra/for-next linus/master v5.9-rc5 v5.9-rc4 v5.9-rc3]
[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/Thomas-Zimmermann/dma-buf-Flag-vmap-ed-memory-as-system-or-I-O-memory/20200914-192712
base:    f965d3ec86fa89285db0fbb983da76ba9c398efa
config: arm-randconfig-r002-20200914 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b2c32c90bab09a6e2c1f370429db26017a182143)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

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

All warnings (new ones prefixed by >>):

>> drivers/gpu/drm/drm_gem_cma_helper.c:179:50: warning: variable 'cma_obj' is uninitialized when used here [-Wuninitialized]
           struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(cma_obj->vaddr);
                                                           ^~~~~~~
   include/linux/dma-buf-map.h:37:13: note: expanded from macro 'DMA_BUF_MAP_INIT_VADDR'
                   .vaddr = (vaddr_), \
                             ^~~~~~
   drivers/gpu/drm/drm_gem_cma_helper.c:178:36: note: initialize the variable 'cma_obj' to silence this warning
           struct drm_gem_cma_object *cma_obj;
                                             ^
                                              = NULL
   1 warning generated.

# https://github.com/0day-ci/linux/commit/7fd403952126005980734501c5d0de5e13b3673b
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Thomas-Zimmermann/dma-buf-Flag-vmap-ed-memory-as-system-or-I-O-memory/20200914-192712
git checkout 7fd403952126005980734501c5d0de5e13b3673b
vim +/cma_obj +179 drivers/gpu/drm/drm_gem_cma_helper.c

   165	
   166	/**
   167	 * drm_gem_cma_free_object - free resources associated with a CMA GEM object
   168	 * @gem_obj: GEM object to free
   169	 *
   170	 * This function frees the backing memory of the CMA GEM object, cleans up the
   171	 * GEM object state and frees the memory used to store the object itself.
   172	 * If the buffer is imported and the virtual address is set, it is released.
   173	 * Drivers using the CMA helpers should set this as their
   174	 * &drm_driver.gem_free_object_unlocked callback.
   175	 */
   176	void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
   177	{
   178		struct drm_gem_cma_object *cma_obj;
 > 179		struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(cma_obj->vaddr);
   180	
   181		cma_obj = to_drm_gem_cma_obj(gem_obj);
   182	
   183		if (gem_obj->import_attach) {
   184			if (cma_obj->vaddr)
   185				dma_buf_vunmap(gem_obj->import_attach->dmabuf, &map);
   186			drm_prime_gem_destroy(gem_obj, cma_obj->sgt);
   187		} else if (cma_obj->vaddr) {
   188			dma_free_wc(gem_obj->dev->dev, cma_obj->base.size,
   189				    cma_obj->vaddr, cma_obj->paddr);
   190		}
   191	
   192		drm_gem_object_release(gem_obj);
   193	
   194		kfree(cma_obj);
   195	}
   196	EXPORT_SYMBOL_GPL(drm_gem_cma_free_object);
   197	

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