Em Fri, 16 Jun 2017 16:39:03 +0900 Gustavo Padovan <gustavo@xxxxxxxxxxx> escreveu: > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx> > > Hi, > > This adds support for Explicit Synchronization of shared buffers in V4L2. > It uses the Sync File Framework[1] as vector to communicate the fences > between kernel and userspace. > > Explicit Synchronization allows us to control the synchronization of > shared buffers from userspace by passing fences to the kernel and/or > receiving them from the the kernel. > > Fences passed to the kernel are named in-fences and the kernel should wait > them to signal before using the buffer. On the other side, the kernel creates > out-fences for every buffer it receives from userspace. This fence is sent back > to userspace and it will signal when the capture, for example, has finished. > > Signalling an out-fence in V4L2 would mean that the job on the buffer is done > and the buffer can be used by other drivers. > > The first patch proposes an userspace API for fences, then on patch 2 > we prepare to the addition of in-fences in patch 3, by introducing the > infrastructure on vb2 to wait on an in-fence signal before queueing the buffer > in the driver. > > Patch 4 fix uvc v4l2 event handling and patch 5 configure q->dev for vivid > drivers to enable to subscribe and dequeue events on it. > > Patches 6-7 enables support to notify BUF_QUEUED events, i.e., let userspace > know that particular buffer was enqueued in the driver. This is needed, > because we return the out-fence fd as an out argument in QBUF, but at the time > it returns we don't know to which buffer the fence will be attached thus > the BUF_QUEUED event tells which buffer is associated to the fence received in > QBUF by userspace. > > Patches 8-9 add support to mark queues as ordered. Finally patches 10 and 11 > add more fence infrastructure to support out-fences and finally patch 12 adds > support to out-fences. > > Changelog are detailed in each patch. > > Please review! Thanks. Just reviewed the series. Most patches look good. I have one additional concern: if the changes here won't cause any bad behaviors if fences is not available for some VB2 non V4L2 client. I'm actually thinking on this: https://patchwork.linuxtv.org/patch/31613/ >From what I saw, after this patch series, someone could try to inconditionally open an out fences fd for a driver. Maybe this should be denied by default, enabling such feature only if the VB2 "client" (e. g. videobuf-v4l2) supports it. Regards, Mauro
