leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

dma-mapping: add a dma_alloc_noncontiguous API

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

19
include/linux/dma-map-ops.h
View File

@@ -22,6 +22,11 @@ struct dma_map_ops {
gfp_t gfp);
void (*free_pages)(struct device *dev, size_t size, struct page *vaddr,
dma_addr_t dma_handle, enum dma_data_direction dir);
struct sg_table *(*alloc_noncontiguous)(struct device *dev, size_t size,
enum dma_data_direction dir, gfp_t gfp,
unsigned long attrs);
void (*free_noncontiguous)(struct device *dev, size_t size,
struct sg_table *sgt, enum dma_data_direction dir);
int (*mmap)(struct device *, struct vm_area_struct *,
void *, dma_addr_t, size_t, unsigned long attrs);
@@ -198,6 +203,20 @@ static inline int dma_mmap_from_global_coherent(struct vm_area_struct *vma,
}
#endif /* CONFIG_DMA_DECLARE_COHERENT */
/*
* This is the actual return value from the ->alloc_noncontiguous method.
* The users of the DMA API should only care about the sg_table, but to make
* the DMA-API internal vmaping and freeing easier we stash away the page
* array as well (except for the fallback case). This can go away any time,
* e.g. when a vmap-variant that takes a scatterlist comes along.
*/
struct dma_sgt_handle {
struct sg_table sgt;
struct page **pages;
};
#define sgt_handle(sgt) \
container_of((sgt), struct dma_sgt_handle, sgt)
int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
void *cpu_addr, dma_addr_t dma_addr, size_t size,
unsigned long attrs);