From patchwork Tue Jul 11 06:30:43 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans Verkuil X-Patchwork-Id: 9834131 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 93D8C60325 for ; Tue, 11 Jul 2017 06:32:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 86F9C22638 for ; Tue, 11 Jul 2017 06:32:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7B11728462; Tue, 11 Jul 2017 06:32:11 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 04BBE22638 for ; Tue, 11 Jul 2017 06:32:11 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B7E6D6E2AF; Tue, 11 Jul 2017 06:31:41 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from lb2-smtp-cloud3.xs4all.net (lb2-smtp-cloud3.xs4all.net [194.109.24.26]) by gabe.freedesktop.org (Postfix) with ESMTPS id A82BC6E2AD for ; Tue, 11 Jul 2017 06:30:52 +0000 (UTC) Received: from marune.fritz.box ([80.101.105.217]) by smtp-cloud3.xs4all.net with ESMTP id jJWk1v00o4hSry801JWrZ7; Tue, 11 Jul 2017 08:30:51 +0200 From: Hans Verkuil To: linux-media@vger.kernel.org Subject: [PATCH 10/11] cec-core.rst: include cec-pin.h and cec-notifier.h Date: Tue, 11 Jul 2017 08:30:43 +0200 Message-Id: <20170711063044.29849-11-hverkuil@xs4all.nl> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170711063044.29849-1-hverkuil@xs4all.nl> References: <20170711063044.29849-1-hverkuil@xs4all.nl> Cc: Maxime Ripard , Hans Verkuil , dri-devel@lists.freedesktop.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Hans Verkuil Include the CEC pin framework documentation by reading cec-pin.h. Include the CEC notifier framework documentation by reading cec-notifier.h. Signed-off-by: Hans Verkuil --- Documentation/media/kapi/cec-core.rst | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/Documentation/media/kapi/cec-core.rst b/Documentation/media/kapi/cec-core.rst index bb066b2b26f8..dc512bdd43c0 100644 --- a/Documentation/media/kapi/cec-core.rst +++ b/Documentation/media/kapi/cec-core.rst @@ -345,3 +345,34 @@ log_addrs->num_log_addrs set to 0. The block argument is ignored when unconfiguring. This function will just return if the physical address is invalid. Once the physical address becomes valid, then the framework will attempt to claim these logical addresses. + +CEC Pin framework +----------------- + +Most CEC hardware operates on full CEC messages where the software provides +the message and the hardware handles the low-level CEC protocol. But some +hardware only drives the CEC pin and software has to handle the low-level +CEC protocol. The CEC pin framework was created to handle such devices. + +Note that due to the close-to-realtime requirements it can never be guaranteed +to work 100%. This framework uses highres timers internally, but if a +timer goes off too late by more than 300 microseconds wrong results can +occur. In reality it appears to be fairly reliable. + +One advantage of this low-level implementation is that it can be used as +a cheap CEC analyser, especially if interrupts can be used to detect +CEC pin transitions from low to high or vice versa. + +.. kernel-doc:: include/media/cec-pin.h + +CEC Notifier framework +----------------- + +Most drm HDMI implementations have an integrated CEC implementation and no +notifier support is needed. But some have independent CEC implementations +that have their own driver. This could be an IP block for an SoC or a +completely separate chip that deals with the CEC pin. For those cases a +drm driver can install a notifier and use the notifier to inform the +CEC driver about changes in the physical address. + +.. kernel-doc:: include/media/cec-notifier.h