[systemd-devel] Automatic multi-seat HP T100 zero client

Lennart Poettering lennart at poettering.net
Wed Mar 20 10:15:05 PDT 2013

On Tue, 19.03.13 17:51, Matthew Cox (m.cox99 at gmail.com) wrote:

> I'm trying to get HP T100s to work for a multiseat configuration. I
> was unable to find the hardware IDs in the database files and believe
> that may fix the issue. Currently maintained are the Plugable usb
> hwid's. One includes the DL-125 chipset, which is the same chipset the
> HP T100 uses. HP T100's DisplayLink HWID (based on the samples I have)
> are 17e9:030b attached to USB root hub of "Standard Microsystems Corp.
> USB 2.0 Hub" with HWID 0424:2514. Can these be added in the same
> manner as the Plugabe 125 to allow for automatic multiseat?

Well, the plugable devices actually are properly recognizable by the hub
already, i.e. Plugable set VID/PID values that it owns, and distuingish
it from any normal hub. Your hub 0424:2514 however looks like a generic
hub chipset that could be built into any normal hub too. If we'd
consider all those hubs automatic seats then things would be weird for
people who happen to have this chipset in a normal hub.

Now, not all is lost. First, there might be other ways to detect the
hub, "udevadm info --attribute-walk" might indicate some other field (for
example ATTR{product}= or so) which indicates that this is a HP

If that's not available, it gets trickier. In many cases, we can do what
we do for the Mimo 720: on the Mimo the hub itself is not recognizable
as mimo device, but the graphics device connected to it contains a
product string that identifies it as Mimo device. Now, normally we
cannot access the subdevice's info during hotplug from the hub's rules,
since the subdevice will show up later only. So, what we do here is
retrigger the hub as soon as we recognized the subdevice. In this second
run we can then easily detect from the hub that it's actually a mimo.

Sounds nasty? It is, but it is quite reliable.

The rules for this are in 71-seat.rules. Please have a look, and check
if you can make sense of it and adapt it to your device.


Lennart Poettering - Red Hat, Inc.

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