Unplugging the main graphics device

[Michael Thayer]

On 22.02.2016 21:29, Dave Airlie wrote:
> On 22 February 2016 at 22:20, Michael Thayer <michael.thayer at oracle.com> wrote:
>> On 19.02.2016 16:16, Michael Thayer wrote:
>>>
>>> I have been experimenting a bit with plugging and unplugging of graphics
>>> devices (using a dummy KMS driver which is udl stripped of the actual
>>> hardware poking) and how the X server copes with that.  It seems to cope
>>> well with a secondary device being removed, but not with the only
>>> graphics device in the system disappearing (in that case the
>>> hot-pluggable device is not deemed to be a GPU device, and therefore not
>>> removable if I understood what is happening correctly).
[...]
> Install driver, ask user to reboot.
>
> Trying to remove the first screen from X is a long and insanity
> inspiring process.
>
> I've spent months hacking up something that lets us migrate stuff from screen A
> to screen B, but it's really messy and the current X server code doesn't lend
> itself to it at all, so I pretty much gave up the last time I tried.

Then perhaps having the place-holder first device in our kernel driver 
is a solution worth considering.  As the main person in charge of the 
kernel DRM tree, is that something you could live with?  I realise that 
making life easier for external drivers is not something which is 
normally done in the Linux kernel, but I think we have a valid reason 
for wanting to update the driver without updating the kernel.  We will 
probably need to go that way with our out-of-tree drivers anyway to 
support older kernel-and-X.Org combinations.

Or am I missing something here?  In theory this could also be done 
directly in the X server, and since you spent months working on this you 
probably already thought about something on these lines.

Regards,

Michael
-- 
Michael Thayer | VirtualBox engineer
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