Re: [PATCH 2/2] iommu/dma: remove most stubs in iommu-dma.h

[Leon Romanovsky <leon@kernel.org>]

On Sun, Sep 22, 2024 at 04:07:35PM +0200, Christoph Hellwig wrote:
> The direct calls from mapping.c all guarded by use_dma_iommu(), so don't
> bother to provide stubs, but instead just expose the prototypes
> unconditionally.

I was afraid to do such a change because of fear that some compiler will
call to the !CONFIG_IOMMU_DMA functions without checking the condition.

Thanks

> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  include/linux/iommu-dma.h | 108 +++-----------------------------------
>  1 file changed, 8 insertions(+), 100 deletions(-)
> 
> diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
> index 7bf145a52d6a1a..508beaa44c39e8 100644
> --- a/include/linux/iommu-dma.h
> +++ b/include/linux/iommu-dma.h
> @@ -14,6 +14,13 @@ static inline bool use_dma_iommu(struct device *dev)
>  {
>  	return dev->dma_iommu;
>  }
> +#else
> +static inline bool use_dma_iommu(struct device *dev)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_IOMMU_DMA */
> +
>  dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
>  		unsigned long offset, size_t size, enum dma_data_direction dir,
>  		unsigned long attrs);
> @@ -58,104 +65,5 @@ void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
>  		int nelems, enum dma_data_direction dir);
>  void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
>  		int nelems, enum dma_data_direction dir);
> -#else
> -static inline bool use_dma_iommu(struct device *dev)
> -{
> -	return false;
> -}
> -static inline dma_addr_t iommu_dma_map_page(struct device *dev,
> -		struct page *page, unsigned long offset, size_t size,
> -		enum dma_data_direction dir, unsigned long attrs)
> -{
> -	return DMA_MAPPING_ERROR;
> -}
> -static inline void iommu_dma_unmap_page(struct device *dev,
> -		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir,
> -		unsigned long attrs)
> -{
> -}
> -static inline int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
> -		int nents, enum dma_data_direction dir, unsigned long attrs)
> -{
> -	return -EINVAL;
> -}
> -static inline void iommu_dma_unmap_sg(struct device *dev,
> -		struct scatterlist *sg, int nents, enum dma_data_direction dir,
> -		unsigned long attrs)
> -{
> -}
> -static inline void *iommu_dma_alloc(struct device *dev, size_t size,
> -		dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
> -{
> -	return NULL;
> -}
> -static inline int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> -		void *cpu_addr, dma_addr_t dma_addr, size_t size,
> -		unsigned long attrs)
> -{
> -	return -EINVAL;
> -}
> -static inline int iommu_dma_get_sgtable(struct device *dev,
> -		struct sg_table *sgt, void *cpu_addr, dma_addr_t dma_addr,
> -		size_t size, unsigned long attrs)
> -{
> -	return -EINVAL;
> -}
> -static inline unsigned long iommu_dma_get_merge_boundary(struct device *dev)
> -{
> -	return 0;
> -}
> -static inline size_t iommu_dma_opt_mapping_size(void)
> -{
> -	return 0;
> -}
> -static inline size_t iommu_dma_max_mapping_size(struct device *dev)
> -{
> -	return 0;
> -}
> -static inline void iommu_dma_free(struct device *dev, size_t size,
> -		void *cpu_addr, dma_addr_t handle, unsigned long attrs)
> -{
> -}
> -static inline dma_addr_t iommu_dma_map_resource(struct device *dev,
> -		phys_addr_t phys, size_t size, enum dma_data_direction dir,
> -		unsigned long attrs)
> -{
> -	return DMA_MAPPING_ERROR;
> -}
> -static inline void iommu_dma_unmap_resource(struct device *dev,
> -		dma_addr_t handle, size_t size, enum dma_data_direction dir,
> -		unsigned long attrs)
> -{
> -}
> -static inline struct sg_table *
> -iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
> -		enum dma_data_direction dir, gfp_t gfp, unsigned long attrs)
> -{
> -	return NULL;
> -}
> -static inline void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> -		struct sg_table *sgt, enum dma_data_direction dir)
> -{
> -}
> -static inline void iommu_dma_sync_single_for_cpu(struct device *dev,
> -		dma_addr_t dma_handle, size_t size,
> -		enum dma_data_direction dir)
> -{
> -}
> -static inline void iommu_dma_sync_single_for_device(struct device *dev,
> -		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
> -{
> -}
> -static inline void iommu_dma_sync_sg_for_cpu(struct device *dev,
> -		struct scatterlist *sgl, int nelems,
> -		enum dma_data_direction dir)
> -{
> -}
> -static inline void iommu_dma_sync_sg_for_device(struct device *dev,
> -		struct scatterlist *sgl, int nelems,
> -		enum dma_data_direction dir)
> -{
> -}
> -#endif /* CONFIG_IOMMU_DMA */
> +
>  #endif /* _LINUX_IOMMU_DMA_H */
> -- 
> 2.45.2
>