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dma-mapping: add a dma_need_unmap helper

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Add helper that allows a driver to skip calling dma_unmap_*
if the DMA layer can guarantee that they are no-nops.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Christoph Hellwig
2025-05-05 10:01:45 +03:00
committed by Marek Szyprowski
parent 433a76207d
commit 5f3b133a23
2 changed files with 23 additions and 0 deletions
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5
include/linux/dma-mapping.h
View File

@@ -406,6 +406,7 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
return dma_dev_need_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
}
bool dma_need_unmap(struct device *dev);
#else /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */
static inline bool dma_dev_need_sync(const struct device *dev)
{
@@ -431,6 +432,10 @@ static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
return false;
}
static inline bool dma_need_unmap(struct device *dev)
{
return false;
}
#endif /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */
struct page *dma_alloc_pages(struct device *dev, size_t size,

18
kernel/dma/mapping.c
View File

@@ -443,6 +443,24 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr)
}
EXPORT_SYMBOL_GPL(__dma_need_sync);
/**
* dma_need_unmap - does this device need dma_unmap_* operations
* @dev: device to check
*
* If this function returns %false, drivers can skip calling dma_unmap_* after
* finishing an I/O. This function must be called after all mappings that might
* need to be unmapped have been performed.
*/
bool dma_need_unmap(struct device *dev)
{
if (!dma_map_direct(dev, get_dma_ops(dev)))
return true;
if (!dev->dma_skip_sync)
return true;
return IS_ENABLED(CONFIG_DMA_API_DEBUG);
}
EXPORT_SYMBOL_GPL(dma_need_unmap);
static void dma_setup_need_sync(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);