2001-03-08 09:22:42

by Terry Barnaby

Subject: Process memory DMA access from devices, kiobuf ?

Hi,

We are doing work with FPGA's and have a Linux driver for a particular
board that has these
devices. For performance reasons the driver has the ability to DMA
directly to process (user)
memory. We have made use of the kiobuf routines such as
"map_user_kiobuf()" to map into
physical memory the user address space.
I note that the RedHat kernels have a patched kernel containing the
kiobuf code but the
standard linux source does not right up to 2.4.2.
Is there a better recommended way to perform DMA access to user memory
from a device
using the Linux kernel ?

Cheers

Terry

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2001-03-08 19:30:58

by Gerd Knorr

Subject: Re: Process memory DMA access from devices, kiobuf ?

Terry Barnaby wrote:
> Hi,
>
> We are doing work with FPGA's and have a Linux driver for a particular
> board that has these
> devices. For performance reasons the driver has the ability to DMA
> directly to process (user)
> memory. We have made use of the kiobuf routines such as
> "map_user_kiobuf()" to map into
> physical memory the user address space.
> I note that the RedHat kernels have a patched kernel containing the
> kiobuf code but the
> standard linux source does not right up to 2.4.2.

Huh? map_user_kiobuf() _is_ present in 2.4.2. See include/linux/iobuf.h

Gerd

--
Get back there in front of the computer NOW. Christmas can wait.
-- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel