On Fri, Oct 11, 2013 at 3:29 PM, John Sheu <s...@google.com> wrote: > Hello folks: > > About the ownership of dmabuf file descriptors that are passed into EGL. > I'm looking in particular at this blurb from the spec: > > * If <target> is EGL_LINUX_DMA_BUF_EXT and eglCreateImageKHR fails, > EGL does not retain ownership of the file descriptor and it is the > responsibility of the application to close it." > > My take on this is that this is different from most users of dmabuf, or even > file descriptors in general. For example, mmap() doesn't own the descriptor > passed to it; and more specifically to dmabufs, neither does (say) > DRM_IOCTL_PRIME_HANDLE_TO_FD, or any of the V4L2 entry points that support > dmabuf (e.g. VIDIOC_QBUF). They all increment the refcount on the > descriptor, not own it. > > Since we're still iterating drafts on the EXT_image_dma_buf_import spec -- > I'd like to see the spec specify that EGL has the similar behavior of taking > a reference, but not owning the descriptor. > > As far as I see, in Mesa, only the Intel stack has implemented > EXT_image_dma_buf_import, and the change would be fairly trivial (removing > dri2_take_dma_buf_ownership), since it eventually just passes the FD down to > DRM_IOCTL_PRIME_HANDLE_TO_FD. And as far as I'm aware, the piglit > conformance tests are the only present consumers. (Maybe the Wayland folks > have something to say about this too.)
We don't use the EXT_image_dma_buf_import extension, we hide all the details in a Wayland specific extensions. But I do agree that the fd life-cycle semantics in the dma_buf extensions are non-standard and it would be cleaner for it to not take ownership of the fd. Kristian > Hopefully the extension's still at a > stage where we can fix up this inconsistency. > > -John Sheu > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
