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i should mention I'm a linux newb. I only use dumb redhat servers at work (barely) but hate windows so much i've got a chromebox and ras pi 4 to try to free myself. and my apps.

i've found that almost ALL usb3=>hdmi devices use special chips by Plugable/DisplayLink that are mostly windows only.

I've found mentions of getting a ras pi 3 working with a usb2.0 displaylink device. But that the only linux drivers are for usb2.0 devices and Ubuntu and you have to jump through hoops to make them work: https://support.displaylink.com/knowledgebase/articles/683482-displaylink-support-for-ubuntu-now-available

I do have a usb 2.0 displaylink device: https://www.amazon.com/gp/product/B004D0QC0A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I've followed this: https://support.displaylink.com/knowledgebase/articles/1883065-using-arm-binaries-on-raspbian-on-raspberry-pi (picking "fake kms" because the std ras pi 4 distrib has no "real") But no luck - xrandr lists nothing extra with -v --listproviders (well, one provider is listed, but no source can be picked - tried 0, 1, 2 - and it's either out of range or can't be selected)

BUT my Chromebox can use my bigger Plugable - no problem at all https://www.amazon.com/gp/product/B00ECDM78E/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

asus chromebox 7265 NGW cpu=Intel core i3-7100u; disk=32gb; ram=8gb ports=usbc, usb3x3, usb2x2, hdmi, microsd, enet, 3.5mm, power cpu=x86-64; kernel=5.4.58; os=ChromeOS; VM=Termina; lxc-container=Debian 10 buster (penguin)

by the way, my ras pi 4 can find the network port, usb drives, midi devices on it. But not the displays.

  • Are there ANY usb3->hdmi devices that aren't DisplayLink ?? (that could work on linux)

  • Is there any hope of a non chromeos linux being able to use DisplayLink some day?

  • Has anyone gotten a usb2.0 -> hdmi device (of any kind) to work on linux?

  • Any ideas on how the heck chromeos is able to use DisplayLink devices ??

thanks for any help :)

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  • argh. this got migrated to ras pi. i'll pick any other linux distrib if i can get usb3=>hdmi working. ras pi is just what i have at the moment. but i'm sure there are smart people here. so i should shut up... – Stephen Hazel Feb 19 at 22:40
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    Welcome to RPi SE - even if you were shanghaied to get here :) I have no answer for you unfortunately, but I don't want you to leave with a poor impression of us. The only thing I can offer is that AFAIK the HDMI port on the RPi is the only way to access video. This may seem odd since RPi is actually a warmed-over GPU chip, but there it is. The other potential obstacle is the closed-source nature of RPi hardware & firmware tend to inhibit 3rd party innovation, tho' there are some working on it. Best of luck! – Seamus Feb 19 at 23:47
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    1) Why not use the normal HDMI? 2) support.displaylink.com/knowledgebase/articles/… tells me that it should be working. 3) you could use a zero (instructables.com/Raspberry-pi-Zero-as-USB-to-HDMI or as an X11 display) – Ljm Dullaart Feb 19 at 23:47
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    Is this article of any interest? Or this one on adding a PCIe interface to the RPi 4? – Seamus Feb 19 at 23:53
  • i have GREAT respect for all stackoverflow sections - especially raspi !! My sadness was that this is a linux wide problem i think?? (displaylink problem) 1) it's so nice to have 2 huge usb3 hubs and swap 2 usb3 lines between my different mini pcs - raspi, chromeos, winblows, another distro linux box soon. hdmi is a pain to unhook and rehook. 2) i tried those steps but displink 4.4 is ooold and the version of rpi they mention is ooold too 3) see 1) :) – Stephen Hazel Feb 20 at 3:28
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Your Chromebook has a USB controller that supports the USB "HDMI Alternate Mode", which allows the USB controller to output HDMI signals instead of USB signals on the USB 3.x connectors' high-speed pairs.

In contrast, your Raspberry Pi 4's USB ports are controlled by a Via Labs VL805 which does not appear to support any of the USB alt-modes for video (HDMI, DisplayPort, MHL, etc.).

There may be other single-board computers (SBCs) out there that compete with the RPi 4 that come with USB controllers that support key USB alt-modes for graphics, but the RPi 4 itself simply doesn't seem to have hardware capable of doing what you want.

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  • is this "hdmi alternate mode" usb controller hardware or software? isn't getting usb3=>hdmi a very common problem on all linux distros? You can use real hdmi just fine. but if you want to do video over usb3 you are just not gonna be able to. Does chromeos have hardware or software that most linux boxes don't ? i'm pretty sure my Plugable usb3 hub has hardware+software in it that send hdmi,vga. But the chromebox is somehow able to send the usb3 according to the latest DisplayLink usb3 protocol... – Stephen Hazel Feb 20 at 3:37
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    HDMI alt mode requires hardware support in the USB chip that controls your USB ports. If your USB circuitry is only designed to send USB signals out the USB connector, and does not have any circuitry for switching over to sending HDMI signals out that connector instead, then your device simply doesn't contain the circuitry necessary for the common ~$15 USB to HDMI adapters, which rely on HDMI alt mode. – Spiff Feb 20 at 4:29
  • hmmm, so if i wiped my chromebox and put the latest ubuntu on it, you guarantee that it could reach my 2 monitors via my Plugable usb3 hub? :) Well, I can always put chromeos back (i think). That'll be a good test. – Stephen Hazel Feb 20 at 16:48
  • ah i see it now. on the chromebox description page: Integrated Intel 4K UHD graphics supports 2x Monitors using HDMI and DisplayPort over Type C - so displayport is built into the usb hardware. GOTCHA (finally - thank you:) – Stephen Hazel Feb 20 at 19:23

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