Computer acting as Thunderbolt "client" and passing through

Question

I have a desktop at home, but also a Thunderbolt enabled laptop. If I wish to utilize my display, audio interface, keyboard and other peripherals, I connect to an old Thunderbolt dock. The issue is that if I want to use the same peripherals on the desktop, I have to unplug them from the dock, and plug them in the desktop. I know I could simply install Thunderbolt card in the desktop and run a second cable to the dock, but I wonder if the following is possible eliminating the need for a dedicated dock.

Would it be possible to connect the laptop to the desktop with Thunderbolt, have the desktop act as a virtual display and USB hub, and then pass through the signal to the desktops usual IO ports? Effectively making the desktop act as a Thunderbolt dock. Possibly enabling features like the desktop recording the display signal from the laptop, or sending picture in picture to the display?

Could this be done with a standard PCIe Thunderbolt card with linux or Windows?

Answer 1

Unfortunately, no. Or at least... not at all easily. The USB devices you mention are Device-Mode USB devices. Your desktop is a Host-Mode USB device. If you connect from your desktop to your laptop, that would be two hosts. Theoretically, it's possible for you to get a separate PCI-E card that could act in device mode (a motherboard almost certainly would not support this, even with a Thunderbolt port). That said, the current "USB Gadget" framework in Linux doesn't support USB Hubs as a gadget device, only first-order devices like keyboards, mice, etc. (trust me, I've searched for this a LOT).

If you wanted to buy a PCI-E Device-mode Thunderbolt card and manually implement that gadget type in Linux, maybe it could work. Maybe.

It'd be a lot easier to just use a KVM Switch that supports Thunderbolt and use that instead of a dock. You could plug your desktop and laptop into it and switch the devices between them with the push of a button. It's also possible that one exists that will auto-swap when another computer is plugged in, but I didn't find one on a cursory look.