[PATCH v7 3/6] [media] vb2: add explicit fence user API

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.com>

Turn the reserved2 field into fence_fd that we will use to send
an in-fence to the kernel and return an out-fence from the kernel to
userspace.

Two new flags were added, V4L2_BUF_FLAG_IN_FENCE, that should be used
when sending a fence to the kernel to be waited on, and
V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence.

v5:
	- keep using reserved2 field for cpia2
	- set fence_fd to 0 for now, for compat with userspace(Mauro)

v4:
	- make it a union with reserved2 and fence_fd (Hans Verkuil)

v3:
	- make the out_fence refer to the current buffer (Hans Verkuil)

v2: add documentation

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
---
 Documentation/media/uapi/v4l/buffer.rst        | 15 +++++++++++++++
 drivers/media/common/videobuf/videobuf2-v4l2.c |  2 +-
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c  |  4 ++--
 include/uapi/linux/videodev2.h                 |  7 ++++++-
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
index ae6ee73f151c..eeefbd2547e7 100644
--- a/Documentation/media/uapi/v4l/buffer.rst
+++ b/Documentation/media/uapi/v4l/buffer.rst
@@ -648,6 +648,21 @@ Buffer Flags
       - Start Of Exposure. The buffer timestamp has been taken when the
 	exposure of the frame has begun. This is only valid for the
 	``V4L2_BUF_TYPE_VIDEO_CAPTURE`` buffer type.
+    * .. _`V4L2-BUF-FLAG-IN-FENCE`:
+
+      - ``V4L2_BUF_FLAG_IN_FENCE``
+      - 0x00200000
+      - Ask V4L2 to wait on fence passed in ``fence_fd`` field. The buffer
+	won't be queued to the driver until the fence signals.
+
+    * .. _`V4L2-BUF-FLAG-OUT-FENCE`:
+
+      - ``V4L2_BUF_FLAG_OUT_FENCE``
+      - 0x00400000
+      - Request a fence to be attached to the buffer. The ``fence_fd``
+	field on
+	:ref:`VIDIOC_QBUF` is used as a return argument to send the out-fence
+	fd to userspace.
 
 
 
diff --git a/drivers/media/common/videobuf/videobuf2-v4l2.c b/drivers/media/common/videobuf/videobuf2-v4l2.c
index fac3cd6f901d..d838524a459e 100644
--- a/drivers/media/common/videobuf/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf/videobuf2-v4l2.c
@@ -203,7 +203,7 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
 	b->timestamp = ns_to_timeval(vb->timestamp);
 	b->timecode = vbuf->timecode;
 	b->sequence = vbuf->sequence;
-	b->reserved2 = 0;
+	b->fence_fd = 0;
 	b->reserved = 0;
 
 	if (q->is_multiplanar) {
diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index e48d59046086..a11a0a2bed47 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -370,7 +370,7 @@ struct v4l2_buffer32 {
 		__s32		fd;
 	} m;
 	__u32			length;
-	__u32			reserved2;
+	__s32			fence_fd;
 	__u32			reserved;
 };
 
@@ -533,7 +533,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer *kp, struct v4l2_buffer32 __user
 		put_user(kp->timestamp.tv_usec, &up->timestamp.tv_usec) ||
 		copy_to_user(&up->timecode, &kp->timecode, sizeof(struct v4l2_timecode)) ||
 		put_user(kp->sequence, &up->sequence) ||
-		put_user(kp->reserved2, &up->reserved2) ||
+		put_user(kp->fence_fd, &up->fence_fd) ||
 		put_user(kp->reserved, &up->reserved) ||
 		put_user(kp->length, &up->length))
 			return -EFAULT;
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 58894cfe9479..2d424aebdd1e 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -933,7 +933,10 @@ struct v4l2_buffer {
 		__s32		fd;
 	} m;
 	__u32			length;
-	__u32			reserved2;
+	union {
+		__s32		fence_fd;
+		__u32		reserved2;
+	};
 	__u32			reserved;
 };
 
@@ -970,6 +973,8 @@ struct v4l2_buffer {
 #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE		0x00010000
 /* mem2mem encoder/decoder */
 #define V4L2_BUF_FLAG_LAST			0x00100000
+#define V4L2_BUF_FLAG_IN_FENCE			0x00200000
+#define V4L2_BUF_FLAG_OUT_FENCE			0x00400000
 
 /**
  * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor
-- 
2.14.3