data transfer from kernel to user space

[Greg KH]

On Tue, Jul 12, 2011 at 12:26:35PM +0530, Amit Nagal wrote:
> After all even for stream-oriented device (as in my case ) , we need
> to copy data from kernel buffer to user-space buffer ,
> and if copy can be avoided via any mechanism , it will be much faster  .

Have you really measured your data rates and determined that the copy is
slowing you down a lot?  If so, how much?

And how would you get data that you are copying from a streaming device
(what type is it), into userspace without doing a copy?  DMA is the only
way that it can be done, would that work for you?

What driver are you using?  What type of device?  And again, have you
measured things to really determine that this is the slow point?
Usually it's the data speed coming in to the device itself that is the
slowest part, and you can't do anything about that in the kernel.

greg k-h