Re: [PATCHv2 10/12] videodev2.h: add V4L2_DEC_CMD_FLUSH

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

On 8/15/19 10:12 AM, Alexandre Courbot wrote:
> On Mon, Aug 12, 2019 at 8:07 PM Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote:
>>
>> Add this new V4L2_DEC_CMD_FLUSH decoder command and document it.
>>
>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> ---
>>  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.
> 
> I'm a bit confused here, isn't this command referred to as
> V4L2_DEC_CMD_STOP in the previous patch?

That was a typo in the previous patch. It really is FLUSH.

Regards,

	Hans

> 
> 
>>
>>  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)
>> --
>> 2.20.1
>>