[RFC v4 16/17] [media] vb2: add out-fence support to QBUF

[Gustavo Padovan]

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>

If V4L2_BUF_FLAG_OUT_FENCE flag is present on the QBUF call we create
an out_fence and send to userspace on the V4L2_EVENT_OUT_FENCE when
the buffer is queued to the driver, or right away if the queue is ordered
both in VB2 and in the driver.

The fence is signaled on buffer_done(), when the job on the buffer is
finished.

v5:
	- delay fd_install to DQ_EVENT (Hans)
	- if queue is fully ordered send OUT_FENCE event right away
	(Brian)
	- rename 'q->ordered' to 'q->ordered_in_driver'
	- merge change to implement OUT_FENCE event here

v4:
	- return the out_fence_fd in the BUF_QUEUED event(Hans)

v3:	- add WARN_ON_ONCE(q->ordered) on requeueing (Hans)
	- set the OUT_FENCE flag if there is a fence pending (Hans)
	- call fd_install() after vb2_core_qbuf() (Hans)
	- clean up fence if vb2_core_qbuf() fails (Hans)
	- add list to store sync_file and fence for the next queued buffer

v2: check if the queue is ordered.

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
 drivers/media/v4l2-core/v4l2-event.c     |  2 ++
 drivers/media/v4l2-core/videobuf2-core.c | 25 +++++++++++++++
 drivers/media/v4l2-core/videobuf2-v4l2.c | 55 ++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c
index 6274e3e174e0..275da224ace4 100644
--- a/drivers/media/v4l2-core/v4l2-event.c
+++ b/drivers/media/v4l2-core/v4l2-event.c
@@ -385,6 +385,8 @@ int v4l2_subscribe_event_v4l2(struct v4l2_fh *fh,
 	switch (sub->type) {
 	case V4L2_EVENT_CTRL:
 		return v4l2_ctrl_subscribe_event(fh, sub);
+	case V4L2_EVENT_OUT_FENCE:
+		return v4l2_event_subscribe(fh, sub, VIDEO_MAX_FRAME, NULL);
 	}
 	return -EINVAL;
 }
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index c7ba67bda5ac..21e2052776c1 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -354,6 +354,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
 			vb->planes[plane].length = plane_sizes[plane];
 			vb->planes[plane].min_length = plane_sizes[plane];
 		}
+		vb->out_fence_fd = -1;
 		q->bufs[vb->index] = vb;
 
 		/* Allocate video buffer memory for the MMAP type */
@@ -934,10 +935,24 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 	case VB2_BUF_STATE_QUEUED:
 		return;
 	case VB2_BUF_STATE_REQUEUEING:
+		/*
+		 * Explicit synchronization requires ordered queues for now,
+		 * so WARN_ON if we are requeuing on an ordered queue.
+		 */
+		if (vb->out_fence)
+			WARN_ON_ONCE(q->ordered_in_driver);
+
 		if (q->start_streaming_called)
 			__enqueue_in_driver(vb);
 		return;
 	default:
+		if (state == VB2_BUF_STATE_ERROR)
+			dma_fence_set_error(vb->out_fence, -ENOENT);
+		dma_fence_signal(vb->out_fence);
+		dma_fence_put(vb->out_fence);
+		vb->out_fence = NULL;
+		vb->out_fence_fd = -1;
+
 		/* Inform any processes that may be waiting for buffers */
 		wake_up(&q->done_wq);
 		break;
@@ -1235,6 +1250,9 @@ static void __enqueue_in_driver(struct vb2_buffer *vb)
 	trace_vb2_buf_queue(q, vb);
 
 	call_void_vb_qop(vb, buf_queue, vb);
+
+	if (!(q->is_output || q->ordered_in_vb2))
+		call_void_bufop(q, send_out_fence, vb);
 }
 
 static int __buf_prepare(struct vb2_buffer *vb, const void *pb)
@@ -1451,6 +1469,7 @@ static struct dma_fence *__set_in_fence(struct vb2_queue *q,
 		}
 
 		q->last_fence = dma_fence_get(fence);
+		call_void_bufop(q, send_out_fence, vb);
 	}
 
 	return fence;
@@ -1840,6 +1859,11 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
 	}
 
 	/*
+	 * Renew out-fence context.
+	 */
+	q->out_fence_context = dma_fence_context_alloc(1);
+
+	/*
 	 * Remove all buffers from videobuf's list...
 	 */
 	INIT_LIST_HEAD(&q->queued_list);
@@ -2171,6 +2195,7 @@ int vb2_core_queue_init(struct vb2_queue *q)
 	spin_lock_init(&q->done_lock);
 	mutex_init(&q->mmap_lock);
 	init_waitqueue_head(&q->done_wq);
+	q->out_fence_context = dma_fence_context_alloc(1);
 
 	if (q->buf_struct_size == 0)
 		q->buf_struct_size = sizeof(struct vb2_buffer);
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 4c09ea007d90..9fb01ddefdc9 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -32,6 +32,11 @@
 
 #include <media/videobuf2-v4l2.h>
 
+struct out_fence_data {
+	int fence_fd;
+	struct file *file;
+};
+
 static int debug;
 module_param(debug, int, 0644);
 
@@ -138,6 +143,38 @@ static void __copy_timestamp(struct vb2_buffer *vb, const void *pb)
 	}
 };
 
+static void __fd_install_at_dequeue_cb(void *data)
+{
+	struct out_fence_data *of = data;
+
+	fd_install(of->fence_fd, of->file);
+	kfree(of);
+}
+
+static void __send_out_fence(struct vb2_buffer *vb)
+{
+	struct video_device *vdev = to_video_device(vb->vb2_queue->dev);
+	struct v4l2_fh *fh = vdev->queue->owner;
+	struct v4l2_event event;
+	struct out_fence_data *of;
+
+	if (vb->out_fence_fd < 0)
+		return;
+
+	memset(&event, 0, sizeof(event));
+	event.type = V4L2_EVENT_OUT_FENCE;
+	event.u.out_fence.index = vb->index;
+	event.u.out_fence.out_fence_fd = vb->out_fence_fd;
+
+	of = kmalloc(sizeof(*of), GFP_KERNEL);
+	of->fence_fd = vb->out_fence_fd;
+	of->file = vb->sync_file->file;
+
+	v4l2_event_queue_fh_with_cb(fh, &event, __fd_install_at_dequeue_cb, of);
+
+	vb->sync_file = NULL;
+}
+
 static void vb2_warn_zero_bytesused(struct vb2_buffer *vb)
 {
 	static bool check_once;
@@ -185,6 +222,12 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
 		return -EINVAL;
 	}
 
+	if (!q->ordered_in_driver && (b->flags & V4L2_BUF_FLAG_OUT_FENCE)) {
+		dprintk(1, "%s: out-fence doesn't work on unordered queues\n",
+			opname);
+		return -EINVAL;
+	}
+
 	return __verify_planes_array(q->bufs[b->index], b);
 }
 
@@ -213,6 +256,8 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
 	b->reserved = 0;
 
 	b->fence_fd = -1;
+	if (vb->out_fence)
+		b->flags |= V4L2_BUF_FLAG_OUT_FENCE;
 	if (vb->in_fence)
 		b->flags |= V4L2_BUF_FLAG_IN_FENCE;
 	else
@@ -456,6 +501,7 @@ static const struct vb2_buf_ops v4l2_buf_ops = {
 	.fill_user_buffer	= __fill_v4l2_buffer,
 	.fill_vb2_buffer	= __fill_vb2_buffer,
 	.copy_timestamp		= __copy_timestamp,
+	.send_out_fence		= __send_out_fence,
 };
 
 /**
@@ -593,6 +639,15 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
 		}
 	}
 
+	if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+		ret = vb2_setup_out_fence(q, b->index);
+		if (ret) {
+			dprintk(1, "failed to set up out-fence\n");
+			dma_fence_put(fence);
+			return ret;
+		}
+	}
+
 	return vb2_core_qbuf(q, b->index, b, fence);
 }
 EXPORT_SYMBOL_GPL(vb2_qbuf);
-- 
2.13.6