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. Actually, we document the m2m draining flow, but the same thing is true for MPEG capture devices like hdpvr that support ENCODER_CMD. So I don't think this is specific to m2m devices. Regards, Hans > > Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > --- > 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> > + </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 > +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 > +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> > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
