DMA using data buffer vmapped in kernel space

[Russell King - ARM Linux]

On Tue, Mar 09, 2010 at 03:45:54PM +0800, Lin Mac wrote:
> I had encounter a similiar problem and I simply allocated a new
> buffer, copy the data, then DMA. It seems slow and stupid.
> 
> I'm wondering wether could I translate the vmap virt to phys(don't
> know how to yet), then use phys_to_virt to get the virt in
> direct-mapped memory region?
> 
> Is there other possible ways?

I think you need to talk to the firmware people... which is unfortunately
orphaned.

What you could do is prepare a patch to allow the firmware support to
export a scatterlist via the struct firmware, and then use that with
dma_map_sg().  Let's hope that the SPI interfaces support scatterlists.