From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752409AbbAMONJ (ORCPT ); Tue, 13 Jan 2015 09:13:09 -0500 Received: from lists.s-osg.org ([54.187.51.154]:49366 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752277AbbAMONG (ORCPT ); Tue, 13 Jan 2015 09:13:06 -0500 Message-ID: <54B527E8.3080004@osg.samsung.com> Date: Tue, 13 Jan 2015 07:12:56 -0700 From: Shuah Khan Organization: Samsung Open Source Group User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Devin Heitmueller CC: Mauro Carvalho Chehab , Hans Verkuil , Prabhakar Lad , "sakari.ailus@linux.intel.com" , Laurent Pinchart , Tim Mester , Linux Media Mailing List , Linux Kernel Subject: Re: [PATCH v3 3/3] media: au0828 remove video and vbi buffer timeout work-around References: <515f84cc1e6e33f647610f1bda154127944e6b52.1421115389.git.shuahkh@osg.samsung.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/12/2015 09:44 PM, Devin Heitmueller wrote: > Hi Shuah, > > On Mon, Jan 12, 2015 at 9:56 PM, Shuah Khan wrote: >> au0828 does video and vbi buffer timeout handling to prevent >> applications such as tvtime from hanging by ensuring that the >> video frames continue to be delivered even when the ITU-656 >> input isn't receiving any data. This work-around is complex >> as it introduces set and clear timer code paths in start/stop >> streaming, and close interfaces. However, tvtime will hang >> without the following tvtime change: > > I'm confused. When we last debated whether this patch would be > accepted, the last message from Mauro said the following: > >> That means that we'll need to keep holding such timeout code for >> years, until all distros update to a new tvtime, of course assuming >> that this is the only one application with such issue. > > In other words, the timeout code has to stay in there since otherwise > it will cause ABI breakage. It's great that Hans has submitted a > patch to improve tvtime, and over the next couple of years that patch > might actually start to appear in distributions. That unfortunately > doesn't change the fact that everybody who updates their kernel (or > has it updated for them as part of their distribution) will go from > "works fine" to "completely broken". > > The driver was working before the VB2 conversion, so if there is now > instability then it's likely that some bug was introduced during the > conversion to VB2. Simply ripping out the timeout code seems like the > wrong approach to addressing a regression likely caused by your own > VB2 conversion patch. > I couldn't reproduce what I was seeing when I did patch v2 series work. What I noticed was that I was seeing a few too many green screens and I had to re-tune xawtv when the timeout code is in place. My thinking was that this timeout handling could be introducing blank green frames when there is no need. However, I can't reproduce the problem on 3.19-rc4 base which is what I am using to test the changes to the patch series. Hence, I am not positive if the timeout code indeed was doing anything bad. I am seeing tvtime hangs without the timeout. I am fine with this patch not going. It does make the code cleaner and also reduces buffer handling during streaming. However, there is a clear regression to tvtime. thanks, -- Shuah -- Shuah Khan Sr. Linux Kernel Developer Open Source Innovation Group Samsung Research America (Silicon Valley) shuahkh@osg.samsung.com | (970) 217-8978