Re: [PATCH v8 08/13] [media] vb2: add explicit fence user API

2018-03-13 Thread Hans Verkuil 
On 03/09/2018 09:49 AM, Gustavo Padovan wrote:
> From: Gustavo Padovan 
> 
> 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
> 
> Signed-off-by: Gustavo Padovan 
> ---
>  Documentation/media/uapi/v4l/buffer.rst | 45 
> +++--
>  drivers/media/common/videobuf2/videobuf2-v4l2.c |  2 +-
>  drivers/media/v4l2-core/v4l2-compat-ioctl32.c   |  4 +--
>  include/uapi/linux/videodev2.h  |  7 +++-
>  4 files changed, 51 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/media/uapi/v4l/buffer.rst 
> b/Documentation/media/uapi/v4l/buffer.rst
> index e2c85ddc990b..49273026740f 100644
> --- 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

fences file descriptors -> a fence file descriptor

> + and vice-versa. On :ref:`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

Missing period at the end of this sentence.

> + 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

on -> in

> + 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

In all other -> For all other buffer

> + ``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``
> +  - 0x0020
> +  - 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.

report -> reports

> +
> +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``
> +  - 0x0040
> +  - 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
> + ` returns. This flag must be set before calling
> + ``VIDIOC_QBUF``. For other ioctls the driver just report the value of

report -> reports

> + the flag.
> +
> +If the creation of the  out-fence  fails ``VIDIOC_QBUF`` returns an

double spaces before and after 'out-fence'.

> + error.
>  
>  
>  
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c 
> b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 68291ba8632d..ad1e032c3bf5 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/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;
>

[PATCH v8 08/13] [media] vb2: add explicit fence user API

2018-03-09 Thread Gustavo Padovan 
From: Gustavo Padovan 

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

Signed-off-by: Gustavo Padovan 
---
 Documentation/media/uapi/v4l/buffer.rst | 45 +++--
 drivers/media/common/videobuf2/videobuf2-v4l2.c |  2 +-
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c   |  4 +--
 include/uapi/linux/videodev2.h  |  7 +++-
 4 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/Documentation/media/uapi/v4l/buffer.rst 
b/Documentation/media/uapi/v4l/buffer.rst
index e2c85ddc990b..49273026740f 100644
--- 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 ` 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``
+  - 0x0020
+  - 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``
+  - 0x0040
+  - 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
+   ` 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/common/videobuf2/videobuf2-v4l2.c 
b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 68291ba8632d..ad1e032c3bf5 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/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 5198c9eeb348..3de2252e3632 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -386,7 +386,7 @@ struct v4l2_buffer32 {
__s32   fd;
} m;
__u32   length;
-   __u32   reserved2;