Hi, On Thu, 16 Feb 2023 at 09:25, Simon Ser <contact@xxxxxxxxxxx> wrote: > On Thursday, February 16th, 2023 at 10:11, Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > > Btw. does this also mean that if you use GETFB2 to get handle A, you > > export that as dmabuf and import in the same open device instance, you > > again get handle A? > > I haven't tested it, but I believe that is correct. > > > IOW, you should never ever export a dmabuf of what you got with > > GETFB2. If one did, one might import it oneself via GBM, breaking all > > reference counting. But you also cannot "just leak" the handle A, > > because if GBM happens to run on a different DRM device opened > > instance, GBM would get a different handle to own. > > > > That's... err. How is a compositor supposed to do transition animation > > from an old FB to its own thing? I guess mmap + glTexImage2D equivalent > > to make a copy of the old FB so one can use it as a texture? > > I think the compositor can export the handle as DMA-BUF, then close the > handle immediately. Then go about its business as usual. Yeah, I think either of those two are the most sensible. We did go back and forth over the semantics a few times - part over mail and part over IRC - and the eventual conclusion was to match GetFB to make it easier for users to transition, but to de-duplicate the handles _within_ the call for consistency with the rest of everything else. It's not the most pleasant compromise, but eh. Cheers, Daniel
