ubuntu-multiseat team mailing list archive

[Richard Hansen <ubuntu-a7x@xxxxxxxxxxxxxxx>]

(please don't top-post; configure your mail client to prefix each line
with '>' and reply inline instead)

On 2014-02-18 06:05, Laércio de Sousa wrote:
> Good question, Richard!
> 
> Let me explain my own example: here in my school, I work with multiseat
> computers consisting of a PCI graphics card with Silicon Motion SM501
> chip and a USB hub with embedded audio device for the secondary seat.
> 
> Since I'm configuring my SM501 card using xorg-x11-video-siliconmotion
> driver, it exposes no framebuffer device or any other kernel device that
> could be handled by logind.

What do you mean by "could be handled by logind"?

All it takes for a device to be associated with a seat is to configure
udev to:
  * Tag it with "seat".  This is required, even for seat0.  (The
    existing udev rules do this properly 99% of the time; exotic
    hardware or unusual circumstances may require you to write your own
    udev rules to tag a device with "seat" or prevent a device from
    being tagged with "seat".)
  * Tag it with the seat name (optional for seat0, required for other
    seats).
  * Set the ID_SEAT property to the seat name (optional for seat0,
    required for other seats.)

In addition, one of the devices must be tagged "master-of-seat".  This
tag signals to logind that the seat hardware is ready (enough) to start
a display manager on that seat.  (Usually the video card is tagged
"master-of-seat" but it could be a different device.  Tagging the video
card is recommended because it is often the only device that is critical
for the seat.)

That's it.  Once udev is configured properly, logind will correctly
advertise the available seats and adjust permissions on device nodes as
users log in/out.  Note that logind doesn't interact with hardware at
all, so there is no such thing as hardware that is or isn't compatible
with or supported by logind.

-Richard


> It's the same scenario one would have with a
> NVIDIA graphics card with proprietary drivers --- but, in this case,
> it's possible that this particular card exposes some other device logind
> can handle. You can run the command "loginctl seat-status <seat>" to get
> a list of current devices logind can handle.
> 
> Because my card can't be handled by logind at all, I can't tag it as
> "master-of-seat", so the best solution in my case is tagging my USB hub
> as "master-of-seat", using the following udev rule:
> 
> # ThinNetworks Audio Hub
> SUBSYSTEM=="usb", ATTR{idVendor}=="05e3", ATTR{idProduct}=="0608",
> TAG+="master-of-seat", ENV{ID_AUTOSEAT}="1", ENV{ID_FOR_SEAT}="XXXX"
> 
> In this example, a new seat named "seat-XXXX" is automatically created
> when I plug the USB hub, in a semi-Plugable fashion.
> 
> Now that the seat is created, the last step is assinging my SM501 card
> to it. This is done with the following xorg config file, which I put in
> /etc/X11/xorg.conf.d folder:
> 
> Section "Device"
>     BusID "PCI:4:1:0"
>     Identifier "videocard_sm501"
>     Driver "siliconmotion"
>     Option "PanelSize" "1360x768"
>     MatchSeat "seat-XXXX"
> EndSection
> Section "Screen"
>     Identifier "screen_sm501"
>     Device "videocard_sm501"
>     DefaultDepth 16
>     MatchSeat "seat-XXXX"
> EndSection
> 
> CANTATE DOMINO CANTICUM NOVUM
> QUIA MIRABILIA FECIT
> 
> Laércio
> 
> 
> 2014-02-17 23:44 GMT-03:00 Richard Hansen <ubuntu-a7x@xxxxxxxxxxxxxxx>:
> 
>> On 2014-02-17 13:07, Laércio de Sousa wrote:
>>> Never mind.
>>>
>>> I've just merged my Launchpad and Ubuntu One accounts and now I can edit
>>> wiki pages.
>> 
>> Excellent.  Thank you for updating the Packages page.
>> 
>> I have a request:  For the patches that you sent upstream, would you
>> mind linking to the mailing list archives from the wiki page?  That will
>> allow people to follow the conversation so far (to get an idea about its
>> progress).
>> 
>> I saw the new step #5 that you added to the instructions.  I'm curious
>> about that step -- I wouldn't have thought that it would be necessary.
>> Does it not work for you if you leave out that xorg config snippet?
>> 
>> Also, step #5 says, "You'll also need to tag another suitable device as
>> master-of-seat in udev".  By "another" do you mean a device other than
>> the video card?  In addition to?  The systemd multiseat page[1] says,
>> "This tag is usually set for the framebuffer device of graphics cards."
>> So I would have expected the master-of-seat instructions in step #2 to
>> be sufficient.
>> 
>> [1] http://www.freedesktop.org/wiki/Software/systemd/multiseat/
>> 
>> -Richard
>> 
>> 
>>>
>>> CANTATE DOMINO CANTICUM NOVUM
>>> QUIA MIRABILIA FECIT
>>>
>>> Laércio
>>>
>>>
>>> 2014-02-17 14:21 GMT-03:00 Laércio de Sousa <lbsousajr@xxxxxxxxx>:
>>>
>>>> Hi there!
>>>>
>>>> I've seen the new wiki page, but I can't edit it (it shows me the
>>>> message "imuttable page", even when I'm logged in).
>>>>
>>>> Any idea?
>>>>
>>>> CANTATE DOMINO CANTICUM NOVUM
>>>> QUIA MIRABILIA FECIT
>>>>
>>>> Laércio
>>>>
>>>>
>>>> 2014-02-14 18:44 GMT-02:00 Richard Hansen <ubuntu-a7x@xxxxxxxxxxxxxxx>:
>>>>> Hi all,
>>>>>
>>>>> I created some wiki pages for the ubuntu-multiseat team, and moved most
>>>>> of the text in the launchpad.net <http://launchpad.net> pages over:
>>>>>
>>>>> https://wiki.ubuntu.com/MultiseatTeam
>>>>>
>>>>> Please feel free to edit the pages as you see fit.
>>>>>
>>>>> Thanks,
>>>>> Richard