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

Gustavo Padovan
2018-01-10T16:10:23Z

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