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).
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with whatever version some guest distribution which is no longer being
updated happens to provide.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).
Re-reading the X server code a couple of days later makes it clear that
this is intended. The question is how I should best deal with this.
Would people be open to having the first graphics device hot-removable
too? Obviously there are other use cases for this, like using
DisplayLink with a headless embedded device. But I realise that the X
server was designed with the assumption that this will not happen. Any
other suggestions? I doubt having a dummy first device which can stay
in place would go down well elsewhere.
Regards,
Michael
--
Michael Thayer | VirtualBox engineer
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