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dma-mapping: add a dma_can_mmap helper 

Add a helper to check if DMA allocations for a specific device can be
mapped to userspace using dma_mmap_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Christoph Hellwig 2019-08-03 13:31:25 +03:00
parent f9f3232a7d
commit e29ccc188f
2 changed files with 28 additions and 0 deletions
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5
include/linux/dma-mapping.h
View File

@ -463,6 +463,7 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size,
unsigned long attrs);
bool dma_can_mmap(struct device *dev);
int dma_supported(struct device *dev, u64 mask);
int dma_set_mask(struct device *dev, u64 mask);
int dma_set_coherent_mask(struct device *dev, u64 mask);
@ -554,6 +555,10 @@ static inline int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
{
return -ENXIO;
}
static inline bool dma_can_mmap(struct device *dev)
{
return false;
}
static inline int dma_supported(struct device *dev, u64 mask)
{
return 0;

23
kernel/dma/mapping.c
View File

@ -222,6 +222,29 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
#endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
}
/**
* dma_can_mmap - check if a given device supports dma_mmap_*
* @dev: device to check
*
* Returns %true if @dev supports dma_mmap_coherent() and dma_mmap_attrs() to
* map DMA allocations to userspace.
*/
bool dma_can_mmap(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
if (IS_ENABLED(CONFIG_ARCH_NO_COHERENT_DMA_MMAP))
return false;
if (dma_is_direct(ops)) {
return dev_is_dma_coherent(dev) ||
IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN);
}
return ops->mmap != NULL;
}
EXPORT_SYMBOL_GPL(dma_can_mmap);
/**
* dma_mmap_attrs - map a coherent DMA allocation into user space
* @dev: valid struct device pointer, or NULL for ISA and EISA-like devices