From patchwork Tue Nov 30 14:15:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tomi Valkeinen X-Patchwork-Id: 517344 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 8F809C433F5 for ; Tue, 30 Nov 2021 14:16:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242110AbhK3OUP (ORCPT ); Tue, 30 Nov 2021 09:20:15 -0500 Received: from perceval.ideasonboard.com ([213.167.242.64]:41004 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242098AbhK3OT7 (ORCPT ); Tue, 30 Nov 2021 09:19:59 -0500 Received: from deskari.lan (91-156-85-209.elisa-laajakaista.fi [91.156.85.209]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 660BC181E; Tue, 30 Nov 2021 15:16:37 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1638281798; bh=8TJugrUWCyKKW9TOvD/ZZtkomjVXNlJhQvIy6/Ae+Xo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ge3Umjh3PZ9TMXyr7GLcFjboIyCQe2X9hRGZFefyIwBgYn+4shwWJDxf+0IdSUZ8I VtibyJHAkEOWaVe/g6HjBTCY1CCUyjTH2amW78luJXgDys37RzGA1+qziN5JtYLxDm IoimOYfX7iruScUZh64tbFTtRKm1AVDgmW/D7Sgw= From: Tomi Valkeinen To: linux-media@vger.kernel.org, sakari.ailus@linux.intel.com, Jacopo Mondi , Laurent Pinchart , niklas.soderlund+renesas@ragnatech.se, Mauro Carvalho Chehab , Hans Verkuil , Pratyush Yadav Cc: Tomi Valkeinen Subject: [PATCH v10 06/38] media: Documentation: add documentation about subdev state Date: Tue, 30 Nov 2021 16:15:04 +0200 Message-Id: <20211130141536.891878-7-tomi.valkeinen@ideasonboard.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211130141536.891878-1-tomi.valkeinen@ideasonboard.com> References: <20211130141536.891878-1-tomi.valkeinen@ideasonboard.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Add documentation about centrally managed subdev state. Signed-off-by: Tomi Valkeinen --- .../driver-api/media/v4l2-subdev.rst | 28 +++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst index 7736da077fb8..db012729f8e3 100644 --- a/Documentation/driver-api/media/v4l2-subdev.rst +++ b/Documentation/driver-api/media/v4l2-subdev.rst @@ -518,6 +518,34 @@ The :c:func:`v4l2_i2c_new_subdev` function will call :c:type:`i2c_board_info` structure using the ``client_type`` and the ``addr`` to fill it. +Centrally managed subdev active state +------------------------------------- + +Traditionally V4L2 subdev drivers maintained internal state for the active +configuration for the subdev. This is often implemented as an array of struct +v4l2_mbus_framefmt, one entry for each pad. + +In addition to the active configuration, each subdev filehandle has an array of +struct v4l2_subdev_pad_config, managed by V4L2 core, which contains the TRY +configuration. + +To simplify the subdev drivers the V4L2 subdev API now optionally supports a +centrally managed active configuration. A subdev driver must use +v4l2_subdev_init_finalize() to initialize the active state between calls to +media_entity_pads_init() and v4l2_*_register_subdev(), and must call +v4l2_subdev_cleanup() to free the state. + +The active state must be locked before access, and that can be done with +v4l2_subdev_lock_state() or v4l2_subdev_lock_active_state(). + +The V4L2 core will pass either the TRY or ACTIVE state to various subdev ops. +Unfortunately not all the subdev drivers comply with this yet, and may pass +NULL for the ACTIVE case. This is only a problem for subdev drivers which use +the centrally managed active state and are used in media pipelines with older +subdev drivers. In these cases the called subdev ops must also handle the NULL +case. This can be easily managed by the use of +v4l2_subdev_validate_and_lock_state() helper. + V4L2 sub-device functions and data structures ---------------------------------------------