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dma-mapping: add a dma_alloc_noncontiguous API

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Add a new API that returns a potentiall virtually non-contigous sg_table
and a DMA address.  This API is only properly implemented for dma-iommu
and will simply return a contigious chunk as a fallback.

The intent is that drivers can use this API if either:

 - no kernel mapping or only temporary kernel mappings are required.
   That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING
 - a kernel mapping is required for cached and DMA mapped pages, but
   the driver also needs the pages to e.g. map them to userspace.
   In that sense it is a replacement for some aspects of the recently
   removed and never fully implemented DMA_ATTR_NON_CONSISTENT

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Ricardo Ribalda <ribalda@chromium.org>
This commit is contained in:
Christoph Hellwig 2021-01-28 14:54:18 +01:00
parent 198c50e2cc
commit 7d5b5738d1
4 changed files with 235 additions and 0 deletions
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32
include/linux/dma-mapping.h
View file

@ -144,6 +144,15 @@ u64 dma_get_required_mask(struct device *dev);
size_t dma_max_mapping_size(struct device *dev);
bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
unsigned long dma_get_merge_boundary(struct device *dev);
struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
enum dma_data_direction dir, gfp_t gfp, unsigned long attrs);
void dma_free_noncontiguous(struct device *dev, size_t size,
struct sg_table *sgt, enum dma_data_direction dir);
void *dma_vmap_noncontiguous(struct device *dev, size_t size,
struct sg_table *sgt);
void dma_vunmap_noncontiguous(struct device *dev, void *vaddr);
int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
size_t size, struct sg_table *sgt);
#else /* CONFIG_HAS_DMA */
static inline dma_addr_t dma_map_page_attrs(struct device *dev,
struct page *page, size_t offset, size_t size,
@ -257,6 +266,29 @@ static inline unsigned long dma_get_merge_boundary(struct device *dev)
{
return 0;
}
static inline struct sg_table *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 dma_free_noncontiguous(struct device *dev, size_t size,
struct sg_table *sgt, enum dma_data_direction dir)
{
}
static inline void *dma_vmap_noncontiguous(struct device *dev, size_t size,
struct sg_table *sgt)
{
return NULL;
}
static inline void dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
{
}
static inline int dma_mmap_noncontiguous(struct device *dev,
struct vm_area_struct *vma, size_t size, struct sg_table *sgt)
{
return -EINVAL;
}
#endif /* CONFIG_HAS_DMA */
struct page *dma_alloc_pages(struct device *dev, size_t size,