From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from ams-iport-1.cisco.com ([144.254.224.140]:32229 "EHLO ams-iport-1.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755132Ab1CBJeQ (ORCPT ); Wed, 2 Mar 2011 04:34:16 -0500 Message-ID: <4D6E0F16.5090809@cisco.com> Date: Wed, 02 Mar 2011 10:34:14 +0100 From: "Martin Bugge (marbugge)" MIME-Version: 1.0 To: =?ISO-8859-1?Q?Daniel_Gl=F6ckner?= CC: linux-media@vger.kernel.org Subject: Re: [RFC] HDMI-CEC proposal References: <4D6CC36B.50009@cisco.com> <20110301233806.GA4969@minime.bse> In-Reply-To: <20110301233806.GA4969@minime.bse> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit List-ID: Sender: On 03/02/2011 12:38 AM, Daniel Glöckner wrote: > On Tue, Mar 01, 2011 at 10:59:07AM +0100, Martin Bugge (marbugge) wrote: > >> CEC is a protocol that provides high-level control functions between >> various audiovisual products. >> It is an optional supplement to the High-Definition Multimedia >> Interface Specification (HDMI). >> Physical layer is a one-wire bidirectional serial bus that uses the >> industry-standard AV.link protocol. >> > Apart from CEC being twice as fast as AV.link and using 3.6V > instead of 5V, CEC does look like an extension to the frame format > defined in EN 50157-2-2 for multiple data bytes. > > So, how about adding support for EN 50157-2-* messages as well? > SCART isn't dead yet. > > EN 50157-2-1 is tricky in that it requires devices to override > data bits like it is done for ack bits to announce their status. > There is a single message type with 21 bits. > > For EN 50157-2-2 the only change necessary would be to tell the > application that it has to use AV.link commands instead of CEC > commands. In theory one could mix AV.link and CEC on a single > wire as they can be distinguished by their start bits. > > EN 50157-2-3 allows 7 vendors to register their own applications > with up to 100 data bits per message. I doubt we can support > these if they require bits on the wire to be modified. > As they still didn't make use of the reserved value to extend the > application number space beyond 7, chances are no vendor ever > applied for a number. > > Just my 2 cents. > > Daniel > Hi Daniel and thank you. I haven't read these standards myself but will do so as soon as I get hold of them. But this sounds like a good idea since cec is based on these protocols. I will look into it. Regards, Martin