arm64: remove dummy_dma_ops

Returning NULL from get_arch_dma_ops makes all DMA mapping routines retourn sensible errors, so remove the dummy ops.

Signed-off-by Christoph Hellwig <[email protected]>

---
  arch/arm64/include/asm/dma-mapping.h |  4 +-
  arch/arm64/mm/dma-mapping.c          | 92 ----------------------------
  2 files changed, 1 insertion(+), 95 deletions(-)

arch/arm64/include/asm/dma-mapping.h +1 -3

index b7847eb8a7bb7..3dd7c10efc745 100644
@@ -24,15 +24,13 @@
  #include <xen/xen.h>
  #include <asm/xen/hypervisor.h>
 
-extern const struct dma_map_ops dummy_dma_ops;
-
  static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
  {
  	/*
  	 * We expect no ISA devices, and all other DMA masters are expected to
  	 * have someone call arch_setup_dma_ops at device creation time.
  	 */
-	return &dummy_dma_ops;
+	return NULL;
  }
 
  void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,

arch/arm64/mm/dma-mapping.c +0 -92

index 072c51fb07d73..4fdce2db6f12d 100644
@@ -406,98 +406,6 @@ static int __init atomic_pool_init(void)
  	return -ENOMEM;
  }
 
-/********************************************
- * The following APIs are for dummy DMA ops *
- ********************************************/
-
-static void *__dummy_alloc(struct device *dev, size_t size,
-			   dma_addr_t *dma_handle, gfp_t flags,
-			   unsigned long attrs)
-{
-	return NULL;
-}
-
-static void __dummy_free(struct device *dev, size_t size,
-			 void *vaddr, dma_addr_t dma_handle,
-			 unsigned long attrs)
-{
-}
-
-static int __dummy_mmap(struct device *dev,
-			struct vm_area_struct *vma,
-			void *cpu_addr, dma_addr_t dma_addr, size_t size,
-			unsigned long attrs)
-{
-	return -ENXIO;
-}
-
-static dma_addr_t __dummy_map_page(struct device *dev, struct page *page,
-				   unsigned long offset, size_t size,
-				   enum dma_data_direction dir,
-				   unsigned long attrs)
-{
-	return 0;
-}
-
-static void __dummy_unmap_page(struct device *dev, dma_addr_t dev_addr,
-			       size_t size, enum dma_data_direction dir,
-			       unsigned long attrs)
-{
-}
-
-static int __dummy_map_sg(struct device *dev, struct scatterlist *sgl,
-			  int nelems, enum dma_data_direction dir,
-			  unsigned long attrs)
-{
-	return 0;
-}
-
-static void __dummy_unmap_sg(struct device *dev,
-			     struct scatterlist *sgl, int nelems,
-			     enum dma_data_direction dir,
-			     unsigned long attrs)
-{
-}
-
-static void __dummy_sync_single(struct device *dev,
-				dma_addr_t dev_addr, size_t size,
-				enum dma_data_direction dir)
-{
-}
-
-static void __dummy_sync_sg(struct device *dev,
-			    struct scatterlist *sgl, int nelems,
-			    enum dma_data_direction dir)
-{
-}
-
-static int __dummy_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
-{
-	return 1;
-}
-
-static int __dummy_dma_supported(struct device *hwdev, u64 mask)
-{
-	return 0;
-}
-
-const struct dma_map_ops dummy_dma_ops = {
-	.alloc                  = __dummy_alloc,
-	.free                   = __dummy_free,
-	.mmap                   = __dummy_mmap,
-	.map_page               = __dummy_map_page,
-	.unmap_page             = __dummy_unmap_page,
-	.map_sg                 = __dummy_map_sg,
-	.unmap_sg               = __dummy_unmap_sg,
-	.sync_single_for_cpu    = __dummy_sync_single,
-	.sync_single_for_device = __dummy_sync_single,
-	.sync_sg_for_cpu        = __dummy_sync_sg,
-	.sync_sg_for_device     = __dummy_sync_sg,
-	.mapping_error          = __dummy_mapping_error,
-	.dma_supported          = __dummy_dma_supported,
-};
-EXPORT_SYMBOL(dummy_dma_ops);
-
  static int __init arm64_dma_init(void)
  {
  	if (swiotlb_force == SWIOTLB_FORCE ||

Quoted 2 lines · Christoph Hellwig

Returning NULL from get_arch_dma_ops makes all DMA mapping routines retourn sensible errors, so remove the dummy ops.

Does it? AFAICS all of the non-optional callbacks will still either BUG_ON(!ops) or blindly dereference the null pointer. Have I lost track of another cleanup patch somewhere?

Quoted 7 lines · Robin Murphy

Quoted 2 lines · Christoph Hellwig

Returning NULL from get_arch_dma_ops makes all DMA mapping routines retourn sensible errors, so remove the dummy ops.

Does it? AFAICS all of the non-optional callbacks will still either BUG_ON(!ops) or blindly dereference the null pointer. Have I lost track of another cleanup patch somewhere?

First thing any driver needs to do is dma_set_mask, which first calls dma_supported:

static inline int dma_supported(struct device *dev, u64 mask)

{
         const struct dma_map_ops *ops = get_dma_ops(dev);

	if (!ops)
		return 0;
	...
}