[RFC PATCH] drm/syncobj: add IOCTL to register an eventfd for a timeline

[Christian König]

Am 10.10.22 um 11:13 schrieb Simon Ser:
> On Sunday, October 9th, 2022 at 20:00, Christian König <christian.koenig at amd.com> wrote:
>
>> Am 09.10.22 um 16:40 schrieb Simon Ser:
>>
>>> Introduce a new DRM_IOCTL_SYNCOBJ_TIMELINE_REGISTER_EVENTFD IOCTL
>>> which signals an eventfd when a timeline point completes.
>> I was entertaining the same though for quite a while, but I would even
>> go a step further and actually always base the wait before signal
>> functionality of the drm_syncobj and the eventfd functionality. That
>> would save us quite a bit of complexity I think.
> Hm what do you mean exactly? I'm not sure I'm following.

Essentially we have the syncobj_wait_entry structure which is added to 
the list whenever somebody starts to wait for a sequence which hasn't 
materialized yet.

Instead of extending this maybe just completely nuke the 
syncobj_wait_entry handling and replace it with your implementation here.

Absolutely not a must have, but might be easier to maintain in the long 
term.

Regards,
Christian.

>
>> As a general note I think the name
>> DRM_IOCTL_SYNCOBJ_TIMELINE_REGISTER_EVENTFD is just to long, just make
>> that DRM_IOCTL_SYNCOBJ_EVENTFD. Same for the function names as well.
> Agreed.
>
>> Additional to that I think we should also always have a graceful
>> handling for binary syncobjs. So please try to avoid making this special
>> for the timeline case (the timeline case should of course still be
>> supported).
> This makes sense to me.