From patchwork Wed Dec 7 10:58:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sakari Ailus X-Patchwork-Id: 13066979 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 673D6C352A1 for ; Wed, 7 Dec 2022 10:58:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229603AbiLGK6H (ORCPT ); Wed, 7 Dec 2022 05:58:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229643AbiLGK6D (ORCPT ); Wed, 7 Dec 2022 05:58:03 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82CD3DF11 for ; Wed, 7 Dec 2022 02:58:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1670410682; x=1701946682; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=0qjqEEAOOB/REGpln7EoIYdnP77LDKiwQUgPjK8YUp0=; b=HFyeN3VKu55FzoDcbsBathyb3Cn/Pxw4/8BRAqX6DBpBXT6jz4qCO8Vq t4wvzARFW+wMITNKR6IjSZxjMcXS9T8ONL49o89/E4gfJVIPrUkPJ1mGV oVY4/sXFm7iNJ5dYT3GK1y8AZeWYLv0nDqbNqxsr3VwE8b67/TWGHDuNP HGjWJtJ+1096HEW2msZGm+7uvKI+QrO1Kc7Fw7kmg7to9K1FDHT/yjN97 s76RBby1gbJj+NU4vwCU3plMRsLzhQBf7arytIRWXZYBZwjTc7Naf1ccN pkSkB4jtxZt79KnW7EXSa509khM/3f6RjIvSgkrCV2iGH6nKT4hDrBtwP g==; X-IronPort-AV: E=McAfee;i="6500,9779,10553"; a="318005100" X-IronPort-AV: E=Sophos;i="5.96,225,1665471600"; d="scan'208";a="318005100" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Dec 2022 02:57:54 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10553"; a="640207794" X-IronPort-AV: E=Sophos;i="5.96,225,1665471600"; d="scan'208";a="640207794" Received: from punajuuri.fi.intel.com (HELO paasikivi.fi.intel.com) ([10.237.72.43]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Dec 2022 02:57:52 -0800 Received: from punajuuri.localdomain (punajuuri.localdomain [192.168.240.130]) by paasikivi.fi.intel.com (Postfix) with ESMTP id 9D6792029D; Wed, 7 Dec 2022 12:57:49 +0200 (EET) Received: from sailus by punajuuri.localdomain with local (Exim 4.94.2) (envelope-from ) id 1p2s7u-003p87-2i; Wed, 07 Dec 2022 12:58:10 +0200 From: Sakari Ailus To: Tomi Valkeinen Cc: linux-media@vger.kernel.org, Jacopo Mondi , Laurent Pinchart , niklas.soderlund+renesas@ragnatech.se, Mauro Carvalho Chehab , Hans Verkuil , satish.nagireddy@getcruise.com, Tomasz Figa Subject: [PATCH v2 1/1] media: Documentation: Interaction between routes, formats and selections Date: Wed, 7 Dec 2022 12:58:09 +0200 Message-Id: <20221207105809.911482-1-sakari.ailus@linux.intel.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Document how setting up routes interacts with formats and selections. Signed-off-by: Sakari Ailus --- since v1: - Rewording changes based on Tomi's comments. In particular stricter separation between "stream" and "stream ID". .../userspace-api/media/v4l/dev-subdev.rst | 50 ++++++++++++++----- 1 file changed, 37 insertions(+), 13 deletions(-) diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst index 5075b1828b32d..92710bb9a0caa 100644 --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst @@ -406,6 +406,8 @@ pixel array is not rectangular but cross-shaped or round. The maximum size may also be smaller than the BOUNDS rectangle. +.. _format-propagation: + Order of configuration and format propagation --------------------------------------------- @@ -507,12 +509,12 @@ source pads. Streams, multiplexed media pads and internal routing ---------------------------------------------------- -Commonly V4L2 subdevices support only separate video streams, that is, only a -single stream can pass through a media link and a media pad. Thus each pad -contains a format configuration for that single stream. In some cases a subdev -can do stream processing and split a stream into two or compose two streams -into one, but the inputs and outputs for the subdev are still a single stream -per pad. +Simple V4L2 subdevices do not support multiple, unrelated video streams, +and only a single stream can pass through a media link and a media pad. +Thus each pad contains a format and selection configuration for that +single stream. A subdev can do stream processing and split a stream into +two or compose two streams into one, but the inputs and outputs for the +subdev are still a single stream per pad. Some hardware, e.g. MIPI CSI-2, support multiplexed streams, that is, multiple data streams are transmitted on the same bus, which is represented by a media @@ -539,14 +541,33 @@ streams from one end of the link to the other, and subdevices have routing tables which describe how the incoming streams from sink pads are routed to the source pads. -A stream ID (often just "stream") is a media link-local identifier for a stream. +A stream ID is a media link-local identifier for a stream. In other words, a particular stream ID must exist on both sides of a media link, but another stream ID can be used for the same stream at the other side -of the subdevice. +of the subdevice. The same stream ID is used to refer to the stream on +both pads of the link on all ioctls operating on pads. + +A stream at a specific point in the media pipeline is identified by the +sub-devdev and a pad ID-stream ID pair. For subdevices that do not support +multiplexed streams the 'stream' field is always 0. + +Interaction between routes, formats and selections +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The addition of routes to the V4L2 sub-device interface moves the +sub-device formats and selections from pads to pad ID-stream ID pairs. +Besides the usual pad ID, also the stream ID needs to be provided for +setting formats and selections. + +Instead of the sub-device wide merging of streams from all source pads +towards all sink pads, data flows for each route are separate from each +other. Any number of routes from streams on sink pads towards streams on +source pads is allowed, to the extent supported by drivers. For every +stream on a sink pad, however, only a single route is allowed. -A stream at a specific point in the media pipeline is identified with the -subdev and a (pad, stream) pair. For subdevices that do not support -multiplexed streams the 'stream' is always 0. +Stream IDs, part of routes, are configured by using the +:ref:`VIDIOC_SUBDEV_S_ROUTING ` ioctl. This will +also revert the format and selection configuration to device defaults. Configuring streams ^^^^^^^^^^^^^^^^^^^ @@ -565,8 +586,11 @@ Controller API ` setting the routing table will reset all the stream configurations in a media entity. -3) Configure streams. Each route endpoint must be configured -with :ref:`VIDIOC_SUBDEV_S_FMT `. +3) Configure formats and selections. Each route is configured separately +as documented plain subdevices in :ref:``. The stream +ID is set to the same stream ID associated with either sink or source pads +of routes configured using the :ref:`VIDIOC_SUBDEV_S_ROUTING +` ioctl. Multiplexed streams setup example ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^