Hello everyone, I've been doing some latency testing on my sur40 driver, and I've measured over 160 ms of round-trip delay (with an external high-speed camera, delay between lighting up an LED and seeing the on-screen response in the video stream). I'm aware that this value has to factor in screen refresh rates etc., but it still seems to me that at least 100 ms have to be accounted for purely by image acquisition and delivery. My question now is: can any of this latency be caused by my usage of DMA-SG (see [1] ff.), or is this a zero-copy operation, i.e. the data is delivered directly to the V4L2 buffer from the USB host controller? Thanks & best regards, Florian [1] https://git.kernel.org/cgit/linux/kernel/git/mchehab/linux-media.git/tree/drivers/input/touchscreen/sur40.c#n431 -- SENT FROM MY DEC VT50 TERMINAL
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