Re: [PATCH v6 23/36] drm: vmwgfx: fix common struct sg_table related issues

[kernel test robot]

Hi Marek,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20200618]
[also build test ERROR on v5.8-rc1]
[cannot apply to linuxtv-media/master staging/staging-testing drm-exynos/exynos-drm-next drm-intel/for-linux-next linus/master v5.8-rc1 v5.7 v5.7-rc7]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Marek-Szyprowski/DRM-fix-struct-sg_table-nents-vs-orig_nents-misuse/20200619-000417
base:    ce2cc8efd7a40cbd17841add878cb691d0ce0bba
config: x86_64-rhel-7.6 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

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

All error/warnings (new ones prefixed by >>):

   drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c: In function 'vmw_ttm_unmap_from_dma':
>> drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c:365:31: error: incompatible type for argument 2 of 'dma_unmap_sgtable'
     365 |  dma_unmap_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL, 0);
         |                         ~~~~~~^~~~~
         |                               |
         |                               struct sg_table
   In file included from include/linux/dma-buf.h:20,
                    from drivers/gpu/drm/vmwgfx/ttm_object.h:40,
                    from drivers/gpu/drm/vmwgfx/ttm_lock.h:55,
                    from drivers/gpu/drm/vmwgfx/vmwgfx_drv.h:44,
                    from drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c:28:
   include/linux/dma-mapping.h:651:75: note: expected 'struct sg_table *' but argument is of type 'struct sg_table'
     651 | static inline void dma_unmap_sgtable(struct device *dev, struct sg_table *sgt,
         |                                                          ~~~~~~~~~~~~~~~~~^~~
   drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c: In function 'vmw_ttm_map_for_dma':
>> drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c:386:36: error: incompatible type for argument 2 of 'dma_map_sgtable'
     386 |  return dma_map_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL, 0);
         |                              ~~~~~~^~~~~
         |                                    |
         |                                    struct sg_table
   In file included from include/linux/dma-buf.h:20,
                    from drivers/gpu/drm/vmwgfx/ttm_object.h:40,
                    from drivers/gpu/drm/vmwgfx/ttm_lock.h:55,
                    from drivers/gpu/drm/vmwgfx/vmwgfx_drv.h:44,
                    from drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c:28:
   include/linux/dma-mapping.h:628:72: note: expected 'struct sg_table *' but argument is of type 'struct sg_table'
     628 | static inline int dma_map_sgtable(struct device *dev, struct sg_table *sgt,
         |                                                       ~~~~~~~~~~~~~~~~~^~~
>> drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c:387:1: warning: control reaches end of non-void function [-Wreturn-type]
     387 | }
         | ^

vim +/dma_unmap_sgtable +365 drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c

   352	
   353	/**
   354	 * vmw_ttm_unmap_from_dma - unmap  device addresses previsouly mapped for
   355	 * TTM pages
   356	 *
   357	 * @vmw_tt: Pointer to a struct vmw_ttm_backend
   358	 *
   359	 * Used to free dma mappings previously mapped by vmw_ttm_map_for_dma.
   360	 */
   361	static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt)
   362	{
   363		struct device *dev = vmw_tt->dev_priv->dev->dev;
   364	
 > 365		dma_unmap_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL, 0);
   366		vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents;
   367	}
   368	
   369	/**
   370	 * vmw_ttm_map_for_dma - map TTM pages to get device addresses
   371	 *
   372	 * @vmw_tt: Pointer to a struct vmw_ttm_backend
   373	 *
   374	 * This function is used to get device addresses from the kernel DMA layer.
   375	 * However, it's violating the DMA API in that when this operation has been
   376	 * performed, it's illegal for the CPU to write to the pages without first
   377	 * unmapping the DMA mappings, or calling dma_sync_sg_for_cpu(). It is
   378	 * therefore only legal to call this function if we know that the function
   379	 * dma_sync_sg_for_cpu() is a NOP, and dma_sync_sg_for_device() is at most
   380	 * a CPU write buffer flush.
   381	 */
   382	static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt)
   383	{
   384		struct device *dev = vmw_tt->dev_priv->dev->dev;
   385	
 > 386		return dma_map_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL, 0);
 > 387	}
   388	

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