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SubjectRe: [PATCH 2/8] videodev2.h: add V4L2_DEC_CMD_FLUSH
On Fri, Aug 23, 2019 at 4:45 AM Jernej Skrabec <jernej.skrabec@siol.net> wrote:
>
> From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>
> Add this new V4L2_DEC_CMD_FLUSH decoder command and document it.
>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> ---
> Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst | 11 ++++++++++-
> Documentation/media/videodev2.h.rst.exceptions | 1 +
> include/uapi/linux/videodev2.h | 1 +
> 3 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst
> index 57f0066f4cff..0bffef6058f7 100644
> --- a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst
> @@ -208,7 +208,16 @@ introduced in Linux 3.3. They are, however, mandatory for stateful mem2mem decod
> been started yet, the driver will return an ``EPERM`` error code. When
> the decoder is already running, this command does nothing. No
> flags are defined for this command.
> -
> + * - ``V4L2_DEC_CMD_FLUSH``
> + - 4
> + - Flush any held capture buffers. Only valid for stateless decoders,
> + and only if ``V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF`` was set.
> + This command is typically used when the application reached the
> + end of the stream and the last output buffer had the
> + ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag set. This would prevent
> + dequeueing the last capture buffer containing the last decoded frame.
> + So this command can be used to explicitly flush that last decoded
> + frame.

Just for safety, can we also specify that it is valid to call this
command even if no buffer was held (in which case it is a no-op), as
this can help make user-space code simpler?

>
> Return Value
> ============
> diff --git a/Documentation/media/videodev2.h.rst.exceptions b/Documentation/media/videodev2.h.rst.exceptions
> index adeb6b7a15cb..a79028e4d929 100644
> --- a/Documentation/media/videodev2.h.rst.exceptions
> +++ b/Documentation/media/videodev2.h.rst.exceptions
> @@ -434,6 +434,7 @@ replace define V4L2_DEC_CMD_START decoder-cmds
> replace define V4L2_DEC_CMD_STOP decoder-cmds
> replace define V4L2_DEC_CMD_PAUSE decoder-cmds
> replace define V4L2_DEC_CMD_RESUME decoder-cmds
> +replace define V4L2_DEC_CMD_FLUSH decoder-cmds
>
> replace define V4L2_DEC_CMD_START_MUTE_AUDIO decoder-cmds
> replace define V4L2_DEC_CMD_PAUSE_TO_BLACK decoder-cmds
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 4fa9f543742d..91a79e16089c 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -1978,6 +1978,7 @@ struct v4l2_encoder_cmd {
> #define V4L2_DEC_CMD_STOP (1)
> #define V4L2_DEC_CMD_PAUSE (2)
> #define V4L2_DEC_CMD_RESUME (3)
> +#define V4L2_DEC_CMD_FLUSH (4)
>
> /* Flags for V4L2_DEC_CMD_START */
> #define V4L2_DEC_CMD_START_MUTE_AUDIO (1 << 0)
> --
> 2.22.1
>

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