[GTALUG] USB-C/3.1 Video and Linux

[Giles Orr]

On 23 March 2018 at 20:01, Scott Sullivan via talk <talk at gtalug.org> wrote:

> On 2018-03-23 12:50 PM, Giles Orr via talk wrote:
>
>> A couple days ago I got a Best Buy flyer, and they have this item:
>>
>> https://www.bestbuy.ca/en-ca/product/asus-zenscreen-15-6-fhd
>> -60hz-5ms-gtg-ips-lcd-monitor-mb16ac-dark-grey/10737845.aspx <
>> https://www.bestbuy.ca/en-ca/product/asus-zenscreen-15-6-fh
>> d-60hz-5ms-gtg-ips-lcd-monitor-mb16ac-dark-grey/10737845.aspx>?
>>
>> It's a portable IPS LCD screen from Asus.  I have a similar item from
>> about three years ago that has two connectors, one for USB power-only and
>> the other for VGA/HDMI.  There were other models at the time that used only
>> one connector, USB for both data and power - but that required a driver
>> (and would have been painfully slow if it was USB2).
>>
>> But now here's this new model: it's one connector only, USB-C.  And
>> presumably USB3.1.  And USB3.1 can carry video.  But at this point I get
>> lost among the standards and their implementations and which one supports
>> what.  I have an Asus Zenbook (it's Linux-only at this point) that has a
>> USB-C connector, but I suspect it's USB3.0.  So the first question is: how
>> do I check that?  Second, does Linux support video-over-USB3.1?  Do I need
>> a special cable?  Is this "Thunderbolt?"  How can I check if my machine
>> would support this?
>>
>
> The Spec you linked say it's DisplayLink, which is the software based
> video solution that requires a driver.
>
> https://en.wikipedia.org/wiki/DisplayLink
>
> USB-C is only a specification for a cable and connector, and somewhat
> agnostic about the data communications spec used across it. The cables are
> of high enough quality that they can support multiple data communications
> specs, generally referred to as alt-modes.
>
> https://en.wikipedia.org/wiki/USB-C#Alternate_Mode_partner_specifications
>
> Thunderbolt 3 for example co-oped the USB-C cable spec for it's cables,
> much like in the previous generations it co-oped the mini-displayport cable
> spec.
>
> Intel makes a point that a port carrying Thunderbolt 3 should also be
> cross wired with USB 3.X and Display Port hardware to output those signals
> as well.
>
> So if you want a monitor that uses a Type-C connector, your looking for a
> display-port monitor. Which your not likely to find in the portable market
> yet.
>
>
Now that I knew what to look for, re-examination of the text and pictures
shows a couple interesting things: "USB Type-C connectivity with hybrid
signal solution for Type-C and Type-A source compatibility (requires a
DisplayLink driver for Type-A connection)."  So it's implying that it
doesn't need a driver for Type-C.  And looking at the pictures, there's a
"DisplayPort" icon next to one of the buttons on the front.  So ...

My other questions stand:

- how can I figure out what USB protocol (3.0 or 3.1) the type-C connector
on my Linux computer supports?
- (clearer understanding leads to a clearer question here, although I'm
still not sure I'm saying it right) does Linux support DisplayPort video
over USB-C?

-- 
Giles
https://www.gilesorr.com/
gilesorr at gmail.com
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