[media] vb2: add explicit fence user API

Turn the reserved2 field into fence_fd that we will use to send
an in-fence to the kernel or 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.

v6:	- big improvement on doc (Hans Verkuil)

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

Change-Id: Ic52ac856718b716c0eda3cae983e32817f09991e
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Janghyuck Kim <janghyuck.kim@samsung.com>

diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
index ae6ee73f151c658dc613860f2d39da1cac7de0dd..597bcc418df4545935e296fcb0217f66b4a155b4 100644 (file)
--- a/Documentation/media/uapi/v4l/buffer.rst
+++ b/Documentation/media/uapi/v4l/buffer.rst
@@ -301,10 +301,22 @@ struct v4l2_buffer
        elements in the ``planes`` array. The driver will fill in the
        actual number of valid elements in that array.
     * - __u32
-      - ``reserved2``
+      - ``fence_fd``
       -
-      - A place holder for future extensions. Drivers and applications
-       must set this to 0.
+      - Used to communicate fences file descriptors from userspace to kernel
+       and vice-versa. On :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` when sending
+       an in-fence for V4L2 to wait on, the ``V4L2_BUF_FLAG_IN_FENCE`` flag must
+       be used and this field set to the fence file descriptor of the in-fence
+       If the in-fence is not valid ` VIDIOC_QBUF`` returns an error.
+
+        To get an out-fence back from V4L2 the ``V4L2_BUF_FLAG_OUT_FENCE``
+       must be set, the kernel will return the out-fence file descriptor on
+       this field. If it fails to create the out-fence ``VIDIOC_QBUF` returns
+        an error.
+
+       In all other ioctls V4L2 sets this field to -1 if
+       ``V4L2_BUF_FLAG_IN_FENCE`` and/or ``V4L2_BUF_FLAG_OUT_FENCE`` are set,
+       otherwise this field is set to 0 for backward compatibility.
     * - __u32
       - ``reserved``
       -
@@ -648,6 +660,33 @@ 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 the fence passed in the ``fence_fd`` field. The
+       buffer won't be queued to the driver until the fence signals. The order
+       in which buffers are queued is guaranteed to be preserved, so any
+       buffers queued after this buffer will also be blocked until this fence
+       signals. This flag must be set before calling ``VIDIOC_QBUF``. For
+       other ioctls the driver just report the value of the flag.
+
+        If the fence signals the flag is cleared and not reported anymore.
+       If the fence is not valid ``VIDIOC_QBUF`` returns an error.
+
+
+    * .. _`V4L2-BUF-FLAG-OUT-FENCE`:
+
+      - ``V4L2_BUF_FLAG_OUT_FENCE``
+      - 0x00400000
+      - Request for a fence to be attached to the buffer. The driver will fill
+       in the out-fence fd in the ``fence_fd`` field when :ref:`VIDIOC_QBUF
+       <VIDIOC_QBUF>` returns. This flag must be set before calling
+       ``VIDIOC_QBUF``. For other ioctls the driver just report the value of
+       the flag.
+
+        If the creation of the  out-fence  fails ``VIDIOC_QBUF`` returns an
+       error.
 
 
 

diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index 3905c427757402df741ef155170396077d97a547..c717f265e4fe5e63770e0cd059a68a2cba1b094d 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -388,7 +388,7 @@ struct v4l2_buffer32 {
                __s32           fd;
        } m;
        __u32                   length;
-       __u32                   reserved2;
+       __s32                   fence_fd;
        __u32                   reserved;
 };
 
@@ -607,7 +607,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer __user *kp,
            assign_in_user(&up->timestamp.tv_usec, &kp->timestamp.tv_usec) ||
            copy_in_user(&up->timecode, &kp->timecode, sizeof(kp->timecode)) ||
            assign_in_user(&up->sequence, &kp->sequence) ||
-           assign_in_user(&up->reserved2, &kp->reserved2) ||
+           assign_in_user(&up->fence_fd, &kp->fence_fd) ||
            assign_in_user(&up->reserved, &kp->reserved) ||
            get_user(length, &kp->length) ||
            put_user(length, &up->length))

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index d1daba6178d9329b99e648f17b0ccb78eea21c6e..ffd441711b35ff2d026d64f03695173437f949ac 100644 (file)
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -925,7 +925,10 @@ struct v4l2_buffer {
                __s32           fd;
        } m;
        __u32                   length;
-       __u32                   reserved2;
+       union {
+               __s32           fence_fd;
+               __u32           reserved2;
+       };
        __u32                   reserved;
 };
 
@@ -962,6 +965,8 @@ 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