Driver to allow DMA from user space

[Greg KH]

On Mon, Dec 19, 2016 at 06:08:47PM +0200, Ran Shalit wrote:
> Hello,
> 
> I want to use DMA from userspace.

Why?

> I already use dma in kernel, and now I want can create a character
> device which will be responsible for this.

Why?

> The only problem is that I want to use the same memory which was
> allocated in kernel with dma_alloc_coherent.

Why?

> Is it correct to use mmap in order to use the phsyical memory which
> was allocated with dma_alloc_coherent ?
> 
> If it's that simple it can be surely helpful, and the simple driver
> which wraps dma_alloc_coherent can do the job for dmaing from
> userspace.

Have you looked at the uio driver interface?

But again, why?  What problem are you trying to solve here?

thanks,

greg k-h