On Mon, May 25, 2015 at 11:23:44AM +0530, Vinod Koul wrote: > On Thu, May 21, 2015 at 09:34:03PM -0400, Jeremy Trimble wrote: > > Hello all, > > > > I've written a kernel module that allows data to be sent to or received from > > any DMA device that supports the dmaengine API, using simple read()/write() > > calls from userspace. > > > > Motivation: > > > > While doing some work for my master's thesis recently using the Xilinx Zynq > > SoC, I needed a way to stream test data into and out of an FPGA soft-core I was > > developing. I was using the Xilinx AXI DMA soft-core (and its > > dmaengine-compatible driver that I believe is related to Kedareswara rao > > Appana's patch submitted recently). > > > > Although dmaengine provides a versatile in-kernel API, to my knowledge there's > > no direct userspace interface for the case where one wants to simply > > send/receive data through a slave dma channel -- writing a separate > > userspace-facing module would be required. (Or some hack using /dev/kmem.) > > why not use dmatest? I guess that's not the only use case for this. Like we discussed already in the memset-revival patches, you might want to use these kind of features from the user-space for example to set or copy large buffers because the CPU is slower than the DMA controller to do so, or simply to offload these kind of operations. I know some out-of-tree interfaces like this already exist, maybe this driver is the opportunity to come up with the right one :) Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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