Sharing a KMS device

[Troll Berserker]

On 19/09/18 02:42, Keith Packard wrote:
> Troll Berserker <berserker.troll at yandex.com> writes:
> 
>> Hmm. I see that drmDropMaster became conditional:
>>
>>       if (!ms->fd_passed)
>>           drmDropMaster(ms->fd);
> 
> That's actually a fix which is necessary so that the lessee doesn't give
> away control of the whole device.

I've missed that drmSetMaster is also conditional now.
I was thinking that lessee has to perform drmSetMaster in order to use the FD.
Such an asymmetry between the Owner and Lessees seems unfortunate for me.

> 
>> I was thinking that may be it is possible to implement a CUSE driver
>> to expose leased descriptors as /dev/dri/card* devices so that it
>> would be possible to run X server unmodified.
> 
> I suppose it could, but I'm not sure why you'd want to?

To pretend that there are multiple GPUs in a system to reuse multiseat setup methods for the case of multiple GPUs.
Prolly CUSE method wouldn't work even if there was a symmetry, because seats are defined in terms of /sys/devices, not /dev/dri/cards