Is DRM needed to configure a VDMA frame buffer?

Question

i have TPG->VDMA->AXIS to video out with a TC configured with constants.
I've been working through the ZC702 TRD
http://www.wiki.xilinx.com/Zynq+Base+TRD+2015.2
My TPG/VDMA drivers seem to load ok by looking at the kernel log. And, I have a /dev/v4l-subdev0 that shows up. 
I seem to be able to configure the TPG fine and I think I understand what is going on with the TPG driver.
But, for VDMA if I just have it set up as a frame buffer what's the easiest way to configure/enable it? The TRD code is really large/conplicated and trying to figure out what the general methodology is for accessing the VDMA driver from a user space program.

Answer 1

Configuration of VDMA is done in Xilinx Video pipeline driver (using linux dma engine APIs).
Take a look at drivers/media/platform/xilinx/xilinx-dma.c
In devicetree (software/petalinux/subsystems/linux/configs/device-tree/video-cap.dtsi a video node is instantiated -
Userspace application will use this video node to query/queue/dequeue buffers.
video_cap {
compatible = "xlnx,video";
dmas = <&vdma_1 1>;
dma-names = "port0";
<snip>
In above example video node is using vdma_1 1 instance which is VDMA S2MM channel - it takes TPG streaming input and write it to mem.
In V4L2 framework vdma programming is encapsulated and it is not recomended to configure VDMA directly from userspace.
One question: Is you end goal to capture frames from TPG and displaying those on display( using DRM) ?
For reference take a look at video_lib (rdf0286-zc702-zvik-base-trd-2015-2\software\xsdk\projects\video_lib\src\s2m_pipeline.c) source.
Few other relevant links:
https://lwn.net/Articles/447435
http://lists.freedesktop.org/archives/dri-devel/2012-March/019778.html
http://www.wiki.xilinx.com/Xilinx+V4L2+driver
https://archive.fosdem.org/2014/schedule/.../v4l2_frameworks.pdf
-Radhey