[Query] doubt on parameters passed to dma_map_single_attrs() API

From: Sodagudi Prasad
Date: Tue Mar 22 2016 - 06:23:17 EST

Hi All,

Would like to check whether the dma_map_single_attrs() API, can accept ptr variable from high memory or not?
If we pass the memory pointer, which is pointing high memory does not work with virt_to_page API.

10 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
11 size_t size,
12 enum dma_data_direction dir,
13 struct dma_attrs *attrs)
14 {
15 const struct dma_map_ops *ops = get_dma_ops(dev);
16 dma_addr_t addr;
18 kmemcheck_mark_initialized(ptr, size);
19 BUG_ON(!valid_dma_direction(dir));
20 addr = ops->map_page(dev, virt_to_page(ptr),
21 (unsigned long)ptr & ~PAGE_MASK, size,
22 dir, attrs);
<Prasad> using the virt_to_page for the high memory will end up with wrong address.
23 debug_dma_map_page(dev, virt_to_page(ptr),
24 (unsigned long)ptr & ~PAGE_MASK, size,
25 dir, addr, true);
26 return addr;
27 }

The only restriction which is observed that, ptr should point to physically contiguous memory.

So can we pass high memory mapped address to dma_map_single API or not?

-Thanks, Prasad

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