From: Hans Verkuil <hverkuil@xs4all.nl>
To: Gustavo Padovan <gustavo@padovan.org>, linux-media@vger.kernel.org
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Shuah Khan <shuahkh@osg.samsung.com>,
linux-kernel@vger.kernel.org,
Gustavo Padovan <gustavo.padovan@collabora.com>
Subject: Re: [PATCH v3 02/15] [media] vb2: add explicit fence user API
Date: Mon, 11 Sep 2017 12:55:08 +0200 [thread overview]
Message-ID: <c962699d-b160-5d7d-b776-49155711d2b7@xs4all.nl> (raw)
In-Reply-To: <20170907184226.27482-3-gustavo@padovan.org>
On 09/07/2017 08:42 PM, Gustavo Padovan wrote:
> 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.
>
> v2: add documentation
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
> ---
> Documentation/media/uapi/v4l/buffer.rst | 19 +++++++++++++++++++
> drivers/media/usb/cpia2/cpia2_v4l.c | 2 +-
> drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 ++--
> drivers/media/v4l2-core/videobuf2-v4l2.c | 2 +-
> include/uapi/linux/videodev2.h | 4 +++-
> 5 files changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
> index ae6ee73f151c..664507ad06c6 100644
> --- a/Documentation/media/uapi/v4l/buffer.rst
> +++ b/Documentation/media/uapi/v4l/buffer.rst
> @@ -648,6 +648,25 @@ 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 for the next buffer to be queued to V4L2 driver.
> + The fence received back through the ``fence_fd`` field doesn't
> + necessarily relate to the current buffer in the
> + :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. Although, most of the time
> + the fence will relate to the current buffer it can't be guaranteed.
> + So to tell userspace which buffer is associated to the out_fence,
> + one should listen for the ``V4L2_EVENT_BUF_QUEUED`` event that
> + provide the id of the buffer when it is queued to the V4L2 driver.
As mentioned in the previous patch, this flag should just signal that userspace
wants to receive a BUF_QUEUED event with the out-fence for this buffer. It's up
to the driver to ensure the correct ordering of the events.
I'm missing documentation for the new fence_fd field.
It should mention that fence_fd is ignored if the IN_FENCE isn't set. Applications
will set fence_fd (aka reserved2) to 0, which should be fine as long as IN_FENCE
isn't set.
>
>
>
> diff --git a/drivers/media/usb/cpia2/cpia2_v4l.c b/drivers/media/usb/cpia2/cpia2_v4l.c
> index 3dedd83f0b19..6cde686bf44c 100644
> --- a/drivers/media/usb/cpia2/cpia2_v4l.c
> +++ b/drivers/media/usb/cpia2/cpia2_v4l.c
> @@ -948,7 +948,7 @@ static int cpia2_dqbuf(struct file *file, void *fh, struct v4l2_buffer *buf)
> buf->sequence = cam->buffers[buf->index].seq;
> buf->m.offset = cam->buffers[buf->index].data - cam->frame_buffer;
> buf->length = cam->frame_size;
> - buf->reserved2 = 0;
> + buf->fence_fd = -1;
> buf->reserved = 0;
> memset(&buf->timecode, 0, sizeof(buf->timecode));
>
> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> index 821f2aa299ae..d624fb5df130 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;
> };
>
> @@ -533,8 +533,8 @@ 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->reserved, &up->reserved) ||
> + put_user(kp->fence_fd, &up->fence_fd) ||
Could you move this up one line? It's easier to parse this diff if it is clear
that fence_fd replaced reserved2.
> put_user(kp->length, &up->length))
> return -EFAULT;
>
> diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
> index 0c0669976bdc..110fb45fef6f 100644
> --- a/drivers/media/v4l2-core/videobuf2-v4l2.c
> +++ b/drivers/media/v4l2-core/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 = -1;
> b->reserved = 0;
>
> if (q->is_multiplanar) {
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 185d6a0acc06..e5abab9a908c 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -924,7 +924,7 @@ struct v4l2_buffer {
> __s32 fd;
> } m;
> __u32 length;
> - __u32 reserved2;
> + __s32 fence_fd;
> __u32 reserved;
> };
>
> @@ -961,6 +961,8 @@ 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
>
Regards,
Hans
next prev parent reply other threads:[~2017-09-11 10:55 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 18:42 [PATCH v3 00/15] V4L2 Explicit Synchronization support Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 01/15] [media] v4l: Document explicit synchronization behaviour Gustavo Padovan
2017-09-08 2:39 ` Nicolas Dufresne
2017-09-11 10:50 ` Hans Verkuil
2017-09-11 11:01 ` Hans Verkuil
2017-09-11 13:18 ` Gustavo Padovan
2017-09-11 13:26 ` Hans Verkuil
2017-09-11 13:34 ` Gustavo Padovan
2017-09-11 13:35 ` Hans Verkuil
2017-09-07 18:42 ` [PATCH v3 02/15] [media] vb2: add explicit fence user API Gustavo Padovan
2017-09-11 10:55 ` Hans Verkuil [this message]
2017-09-11 11:03 ` Hans Verkuil
2017-10-02 13:42 ` Brian Starkey
2017-10-04 20:12 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 03/15] [media] vb2: check earlier if stream can be started Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 04/15] [media] vb2: add in-fence support to QBUF Gustavo Padovan
2017-10-02 13:43 ` Brian Starkey
2017-09-07 18:42 ` [PATCH v3 05/15] [media] uvc: enable subscriptions to other events Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 06/15] [media] vivid: assign the specific device to the vb2_queue->dev Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 07/15] [media] v4l: add V4L2_EVENT_BUF_QUEUED event Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 08/15] [media] vb2: add .buffer_queued() to notify queueing in the driver Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 09/15] [media] v4l: add support to BUF_QUEUED event Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 10/15] [media] vb2: add 'ordered' property to queues Gustavo Padovan
2017-10-02 13:43 ` Brian Starkey
2017-10-04 20:18 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 11/15] [media] vivid: mark vivid queues as ordered Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 12/15] [media] vb2: add videobuf2 dma-buf fence helpers Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 13/15] [media] vb2: add infrastructure to support out-fences Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 14/15] fs/files: export close_fd() symbol Gustavo Padovan
2017-09-07 18:51 ` Eric Biggers
2017-09-07 20:36 ` Al Viro
2017-09-07 21:22 ` Gustavo Padovan
2017-09-07 22:03 ` Al Viro
2017-09-07 22:09 ` Hans Verkuil
2017-09-07 22:18 ` Gustavo Padovan
2017-09-07 18:42 ` [PATCH v3 15/15] [media] vb2: add out-fence support to QBUF Gustavo Padovan
2017-10-02 13:41 ` [PATCH v3 00/15] V4L2 Explicit Synchronization support Brian Starkey
2017-10-04 20:08 ` Gustavo Padovan
2017-10-13 1:56 ` Brian Starkey
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