From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFA82C10F0F for ; Fri, 5 Apr 2019 10:59:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91ADF217D4 for ; Fri, 5 Apr 2019 10:59:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730802AbfDEK7e (ORCPT ); Fri, 5 Apr 2019 06:59:34 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:33973 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730546AbfDEK7d (ORCPT ); Fri, 5 Apr 2019 06:59:33 -0400 Received: from lupine.hi.pengutronix.de ([2001:67c:670:100:3ad5:47ff:feaf:1a17] helo=lupine) by metis.ext.pengutronix.de with esmtp (Exim 4.89) (envelope-from ) id 1hCMZH-0006bS-94; Fri, 05 Apr 2019 12:59:31 +0200 Message-ID: <1554461965.3060.5.camel@pengutronix.de> Subject: Re: [PATCH v3 1/2] media: docs-rst: Document memory-to-memory video decoder interface From: Philipp Zabel To: Tomasz Figa , linux-media@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Hans Verkuil , Mauro Carvalho Chehab , Pawel Osciak , Alexandre Courbot , Kamil Debski , Andrzej Hajda , Kyungmin Park , Jeongtae Park , Tiffany Lin =?UTF-8?Q?=28=E6=9E=97=E6=85=A7=E7=8F=8A=29?= , Andrew-CT Chen =?UTF-8?Q?=28=E9=99=B3=E6=99=BA=E8=BF=AA=29?= , Stanimir Varbanov , Todor Tomov , Nicolas Dufresne , Paul Kocialkowski , Laurent Pinchart , dave.stevenson@raspberrypi.org, Ezequiel Garcia , Maxime Jourdan Date: Fri, 05 Apr 2019 12:59:25 +0200 In-Reply-To: <20190124100419.26492-2-tfiga@chromium.org> References: <20190124100419.26492-1-tfiga@chromium.org> <20190124100419.26492-2-tfiga@chromium.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:100:3ad5:47ff:feaf:1a17 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-01-24 at 19:04 +0900, Tomasz Figa wrote: > Due to complexity of the video decoding process, the V4L2 drivers of > stateful decoder hardware require specific sequences of V4L2 API calls > to be followed. These include capability enumeration, initialization, > decoding, seek, pause, dynamic resolution change, drain and end of > stream. > > Specifics of the above have been discussed during Media Workshops at > LinuxCon Europe 2012 in Barcelona and then later Embedded Linux > Conference Europe 2014 in Düsseldorf. The de facto Codec API that > originated at those events was later implemented by the drivers we already > have merged in mainline, such as s5p-mfc or coda. > > The only thing missing was the real specification included as a part of > Linux Media documentation. Fix it now and document the decoder part of > the Codec API. > > Signed-off-by: Tomasz Figa > --- > Documentation/media/uapi/v4l/dev-decoder.rst | 1076 +++++++++++++++++ > Documentation/media/uapi/v4l/dev-mem2mem.rst | 5 + > Documentation/media/uapi/v4l/pixfmt-v4l2.rst | 5 + > Documentation/media/uapi/v4l/v4l2.rst | 10 +- > .../media/uapi/v4l/vidioc-decoder-cmd.rst | 40 +- > Documentation/media/uapi/v4l/vidioc-g-fmt.rst | 14 + > 6 files changed, 1135 insertions(+), 15 deletions(-) > create mode 100644 Documentation/media/uapi/v4l/dev-decoder.rst > > diff --git a/Documentation/media/uapi/v4l/dev-decoder.rst b/Documentation/media/uapi/v4l/dev-decoder.rst > new file mode 100644 > index 000000000000..b7db2352ad41 > --- /dev/null > +++ b/Documentation/media/uapi/v4l/dev-decoder.rst > @@ -0,0 +1,1076 @@ > +.. -*- coding: utf-8; mode: rst -*- > + > +.. _decoder: > + > +************************************************* > +Memory-to-memory Stateful Video Decoder Interface > +************************************************* > + [...] > + > +Drain > +===== > + [...] > + > +3. Once all the ``OUTPUT`` buffers queued before the ``V4L2_DEC_CMD_STOP`` call > + are dequeued and the last ``CAPTURE`` buffer is dequeued, the decoder is > + stopped and it will accept, but not process, any newly queued ``OUTPUT`` > + buffers until the client issues any of the following operations: > + [...] > + > +.. note:: > + > + Once the drain sequence is initiated, the client needs to drive it to > + completion, as described by the steps above, unless it aborts the process by > + issuing :c:func:`VIDIOC_STREAMOFF` on any of the ``OUTPUT`` or ``CAPTURE`` > + queues. The client is not allowed to issue ``V4L2_DEC_CMD_START`` or > + ``V4L2_DEC_CMD_STOP`` again while the drain sequence is in progress and they > + will fail with -EBUSY error code if attempted. Should the V4L2_DEC_CMD_STOP documentation in Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst: * - ``V4L2_DEC_CMD_STOP`` - 1 - Stop the decoder. When the decoder is already stopped, this       command does nothing. be updated to mention that for mem2mem decoders this not only does nothing, but returns an -EBUSY error return value? Also, if V4L2_DEC_CMD_STOP_IMMEDIATELY is set, should the decoder drop all pending buffers and signal EOS immediately? Should this be mentioned here? > + Although mandatory, the availability of decoder commands may be queried > + using :c:func:`VIDIOC_TRY_DECODER_CMD`. Do the TRY_DECODER_CMD also return -EBUSY during the draining phase? regards Philipp