Hi Philipp,
I finally got around to reviewing this patch series. Sorry for the delay, but
here are my comments:
On 04/20/2015 10:28 AM, Philipp Zabel wrote:
> Document the interaction between VIDIOC_DECODER_CMD V4L2_DEC_CMD_STOP and
> VIDIOC_ENCODER_CMD V4L2_ENC_CMD_STOP to start the draining, the V4L2_EVENT_EOS
> event signalling all capture buffers are finished and ready to be dequeud,
> the new V4L2_BUF_FLAG_LAST buffer flag indicating the last buffer being
> dequeued
> from the capture queue, and the poll and VIDIOC_DQBUF ioctl return values once
> the queue is drained.
>
> Signed-off-by: Philipp Zabel <p.za...@pengutronix.de>
> ---
> Changes since v4:
> - Split out documentation changes into a separate patch
> - Changed wording following Pawel's suggestions.
> ---
> Documentation/DocBook/media/v4l/io.xml | 10 ++++++++++
> Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml | 9 ++++++++-
> Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml | 8 +++++++-
> Documentation/DocBook/media/v4l/vidioc-qbuf.xml | 8 ++++++++
> 4 files changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/io.xml
> b/Documentation/DocBook/media/v4l/io.xml
> index 1c17f80..f561037 100644
> --- a/Documentation/DocBook/media/v4l/io.xml
> +++ b/Documentation/DocBook/media/v4l/io.xml
> @@ -1129,6 +1129,16 @@ in this buffer has not been created by the CPU but by
> some DMA-capable unit,
> in which case caches have not been used.</entry>
> </row>
> <row>
> + <entry><constant>V4L2_BUF_FLAG_LAST</constant></entry>
> + <entry>0x00100000</entry>
> + <entry>Last buffer produced by the hardware. mem2mem codec drivers
> +set this flag on the capture queue for the last buffer when the
> +<link linkend="vidioc-querybuf">VIDIOC_QUERYBUF</link> or
> +<link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl is called. Any
> subsequent
> +call to the <link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl will not
> block
> +anymore, but return an &EPIPE;.</entry>
As Kamil mentioned in his review, we should allow for bytesused == 0 here.
> + </row>
> + <row>
> <entry><constant>V4L2_BUF_FLAG_TIMESTAMP_MASK</constant></entry>
> <entry>0x0000e000</entry>
> <entry>Mask for timestamp types below. To test the
> diff --git a/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml
> b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml
> index 9215627..6502d82 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml
> @@ -197,7 +197,14 @@ be muted when playing back at a non-standard speed.
> this command does nothing. This command has two flags:
> if <constant>V4L2_DEC_CMD_STOP_TO_BLACK</constant> is set, then the decoder
> will
> set the picture to black after it stopped decoding. Otherwise the last image
> will
> -repeat. If <constant>V4L2_DEC_CMD_STOP_IMMEDIATELY</constant> is set, then
> the decoder
> +repeat. mem2mem decoders will stop producing new frames altogether. They
> will send
> +a <constant>V4L2_EVENT_EOS</constant> event when the last frame has been
> decoded
> +and all frames are ready to be dequeued and will set the
> +<constant>V4L2_BUF_FLAG_LAST</constant> buffer flag on the last buffer of the
Make a note here as well that the last buffer might be an empty buffer.
> +capture queue to indicate there will be no new buffers produced to dequeue.
> Once
> +this flag was set, the <link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl
> +will not block anymore, but return an &EPIPE;.
> +If <constant>V4L2_DEC_CMD_STOP_IMMEDIATELY</constant> is set, then the
> decoder
> stops immediately (ignoring the <structfield>pts</structfield> value),
> otherwise it
> will keep decoding until timestamp >= pts or until the last of the pending
> data from
> its internal buffers was decoded.
> diff --git a/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml
> b/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml
> index 0619ca5..3cdb841 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml
> @@ -129,7 +129,13 @@ this command.</entry>
> encoding will continue until the end of the current <wordasword>Group
> Of Pictures</wordasword>, otherwise encoding will stop immediately.
> When the encoder is already stopped, this command does
> -nothing.</entry>
> +nothing. mem2mem encoders will send a <constant>V4L2_EVENT_EOS</constant>
> event
> +when the last frame has been decoded and all frames are ready to be dequeued
> and
> +will set the <constant>V4L2_BUF_FLAG_LAST</constant> buffer flag on the last
> +buffer of the capture queue to indicate there will be no new buffers
> produced to
Ditto.
> +dequeue. Once this flag was set, the
> +<link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl will not block anymore,
> +but return an &EPIPE;.</entry>
> </row>
> <row>
> <entry><constant>V4L2_ENC_CMD_PAUSE</constant></entry>
> diff --git a/Documentation/DocBook/media/v4l/vidioc-qbuf.xml
> b/Documentation/DocBook/media/v4l/vidioc-qbuf.xml
> index 3504a7f..6cfc53b 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-qbuf.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-qbuf.xml
> @@ -186,6 +186,14 @@ In that case the application should be able to safely
> reuse the buffer and
> continue streaming.
> </para>
> </listitem>
> + <term><errorcode>EPIPE</errorcode></term>
> + <listitem>
> + <para><constant>VIDIOC_DQBUF</constant> returns this on an empty
> +capture queue for mem2mem codecs if a buffer with the
> +<constant>V4L2_BUF_FLAG_LAST</constant> was already dequeued and no new
> buffers
> +are expected to become available.
> + </para>
> + </listitem>
> </varlistentry>
> </variablelist>
> </refsect1>
>
Regards,
Hans
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