this post was submitted on 03 May 2025
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That's cool and everything, yet we have an itsy-bitsy tiny problem: iirc, there are like 3.5 vendors that have opted into dp alt mode support, and each one I know of kinda sucks. I suppose it might be possible to simply enable it in software by changing the devicetree on usb3 devices or something if the port the vendor decided to route is the one multiplexed with dp, but I wouldn't hold my breath.
Fairphones support it :) I actually tested this out earlier (the initial screen mirroring implementation that was added in android 15) and it worked well. USB hub functionality works too with mouse and keyboard being plugged into the screen.
That's because there's not really any reason for them to implement it. This will give them a reason.
Explain the DP alt mode
That lets a USB C port function as a DisplayPort output so you can connect the phone to a monitor without using some laggy wireless streaming crap.
I thought that all USB-C phones had that feature
Samsungs mostly, also shift and a few older models. Although, some have a crutch called displaylink, which basically encapsulates video signal over USB in software, while dp alt mode kinda* connects those same wires to the displayport output of the SoC (which is better due to having little to no overhead as well as ~no need for specialized overcomplicated hardware).
Also, some of the older models, like my beloved oneplus 6, don't even support USB 3, so dp alt mode is physically impossible for those.
* iirc, on qualcomms at least the SoC itself multiplexes USB 3 with dp (as in, it can be configured to output usb3 or dp on the same data lines), but I'm not sure how the switching itself is triggered, so there may or may not be a need to add another IC that'll handle communications over CC lines and tell the SoC when to use which. I personally suppose the SoCs should be able to handle everything themselves, tho.
Oh neat, I thought it was all DP-protocol via software over USB-C. I didn't know it could be wired straight into display hardware too