Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753086AbXJBHEw (ORCPT ); Tue, 2 Oct 2007 03:04:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751134AbXJBHEo (ORCPT ); Tue, 2 Oct 2007 03:04:44 -0400 Received: from toronto053.server4you.de ([62.75.220.53]:40064 "EHLO toronto053.server4you.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbXJBHEn (ORCPT ); Tue, 2 Oct 2007 03:04:43 -0400 X-Greylist: delayed 1151 seconds by postgrey-1.27 at vger.kernel.org; Tue, 02 Oct 2007 03:04:43 EDT Message-ID: <4701E902.3070104@monom.org> Date: Tue, 02 Oct 2007 08:45:22 +0200 From: Daniel Wagner User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: =?UTF-8?B?S3Jpc3RpYW4gSMO4Z3NiZXJn?= CC: Pieter Palmers , =?UTF-8?B?S3Jpc3RpYW4gSMO4Z3NiZXJn?= , Stefan Richter , linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] firewire: adopt read cycle timer ABI from raw1394 References: <4700BE87.2040107@joow.be> <59ad55d30710010903y76330624ka45747c0b5983cfd@mail.gmail.com> In-Reply-To: <59ad55d30710010903y76330624ka45747c0b5983cfd@mail.gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1088 Lines: 22 >>> Pieter, do applications like yours need the cycle counter only for a few >>> predetermined packets or for each and every packet? >> We need it for every packet for two reasons: >> 1) it's the only way to determine how many packets were dropped when >> packet drops are flagged in the callback > > Your application should know what the timestamp should be for each iso > receive callback and if you see a larger value than expected you can > use that to calculate how many cycles were lost. That might not work if the device is synchronized to SPDIF for example. In this case it is possible (and very likely) that the two clock domains (SPDIF and the firewire bus) drift. The time difference between two timestamps do not have to be the same all the time. So it can be hard (possible?) to predict the next timestamp correctly. daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/