DMA-API attr - DMA_ATTR_NO_KERNEL_MAPPING

[Pankaj Suryawanshi <pankajssuryawanshi@gmail.com>]

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Hello,

I am writing driver in which I used DMA_ATTR_NO_KERNEL_MAPPING attribute
for cma allocation using dma_alloc_attr(), as per kernel docs
https://www.kernel.org/doc/Documentation/DMA-attributes.txt  buffers
allocated with this attribute can be only passed to user space by calling
dma_mmap_attrs().

how can I mapped in kernel space (after dma_alloc_attr with
DMA_ATTR_NO_KERNEL_MAPPING ) ?

For example.

1. virtual_addr = dma_alloc_attr(device, size,, phys, GFP_KERNEL,
DMA_ATTR_NO_KERNEL_MAPPING );
2. Now i can use phys for driver as physical address and i am using in
drivers, working fine.
3. Now i want to use virtual address in kernel space(in some cases virtual
address required in my driver), not allow to use virtual_addr in kernel
space because DMA_ATTR_NO_KERNEL_MAPPING, How can i mapped again to kernel
space ?

How can i used DMA_ATTR_NO_KERNEL_MAPPING  and mapped some area for kernel
space when needed ?

Is there any apis available ? or improvement is required in linux kernel
dma-apis ?

Regards,
Pankaj

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