Unplugging the main graphics device

[Michael Thayer]

Hello,

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).

This is interesting for me because I am looking at putting a KMS driver 
for the VirtualBox video device into the upstream kernel, but would like 
to be able to update the driver at run-time, so that we are not stuck 
with whatever version some guest distribution which is no longer being 
updated happens to provide.  My first idea for handling this was to 
simulate a device unplug so that the old driver could be removed and the 
new one added.  (Not sure if I am handling the hotplug right in the 
vboxvideo driver yet of course, but I assume that my dummy driver, which 
just copies code from udl, does get it right.)

I will take a look at this when I get a chance of course, but I thought 
I would write to the list before that in case anyone else has thoughts, 
ideas or fixes (potenially including how I could better handle the 
driver update).

Regards,

Michael
-- 
Michael Thayer | VirtualBox engineer
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