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SubjectRe: [PATCH 3/5] dma: Introduce dma_max_mapping_size()
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On 1/29/19 2:43 AM, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> The function returns the maximum size that can be mapped
> using DMA-API functions. The patch also adds the
> implementation for direct DMA and a new dma_map_ops pointer
> so that other implementations can expose their limit.
>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> Documentation/DMA-API.txt | 8 ++++++++
> include/linux/dma-mapping.h | 16 ++++++++++++++++
> kernel/dma/direct.c | 11 +++++++++++
> 3 files changed, 35 insertions(+)
>
> diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
> index e133ccd60228..acfe3d0f78d1 100644
> --- a/Documentation/DMA-API.txt
> +++ b/Documentation/DMA-API.txt
> @@ -195,6 +195,14 @@ Requesting the required mask does not alter the current mask. If you
> wish to take advantage of it, you should issue a dma_set_mask()
> call to set the mask to the value returned.
>
> +::
> +
> + size_t
> + dma_direct_max_mapping_size(struct device *dev);
> +
> +Returns the maximum size of a mapping for the device. The size parameter
> +of the mapping functions like dma_map_single(), dma_map_page() and
> +others should not be larger than the returned value.
>
> Part Id - Streaming DMA mappings
> --------------------------------
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index f6ded992c183..a3ca8a71a704 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -130,6 +130,7 @@ struct dma_map_ops {
> enum dma_data_direction direction);
> int (*dma_supported)(struct device *dev, u64 mask);
> u64 (*get_required_mask)(struct device *dev);
> + size_t (*max_mapping_size)(struct device *dev);
> };
>
> #define DMA_MAPPING_ERROR (~(dma_addr_t)0)
> @@ -257,6 +258,8 @@ static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
> }
> #endif
>
> +size_t dma_direct_max_mapping_size(struct device *dev);
> +
> #ifdef CONFIG_HAS_DMA
> #include <asm/dma-mapping.h>
>
> @@ -440,6 +443,19 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
> return 0;
> }
>
> +static inline size_t dma_max_mapping_size(struct device *dev)
> +{
> + const struct dma_map_ops *ops = get_dma_ops(dev);
> + size_t size = SIZE_MAX;
> +
> + if (dma_is_direct(ops))
> + size = dma_direct_max_mapping_size(dev);
> + else if (ops && ops->max_mapping_size)
> + size = ops->max_mapping_size(dev);
> +
> + return size;
> +}
> +
> void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
> gfp_t flag, unsigned long attrs);
> void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 355d16acee6d..6310ad01f915 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -380,3 +380,14 @@ int dma_direct_supported(struct device *dev, u64 mask)
> */
> return mask >= __phys_to_dma(dev, min_mask);
> }
> +
> +size_t dma_direct_max_mapping_size(struct device *dev)
> +{
> + size_t size = SIZE_MAX;
> +
> + /* If SWIOTLB is active, use its maximum mapping size */
> + if (is_swiotlb_active())
> + size = swiotlb_max_mapping_size(dev);
> +
> + return size;
> +}

When I build with these patches and with the virtio devices as modules I
get a build failure. Looks like this needs an EXPORT_SYMBOL() (I'm
assuming EXPORT_SYMBOL for DMA functions and not EXPORT_SYMBOL_GPL?).

Thanks,
Tom

>
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