Re: Question regarding DMA xfer to user space directly

[Alan Cox]

On Maw, 2003-07-08 at 15:50, Alan Shih wrote:
> Is there a provision in MM for DMA transfer to user space directly without
> allocating a kernel buffer?

Yes. Its used both for O_DIRECT I/O (direct to disk I/O from userspace)
and for things like tv capture cards. The kernel allows a driver to pin
user pages and obtain mappings for them. Note that for large systems 
user pages may be above the 32bit boundary so you need DAC capable
hardware to get the best results