From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 448BE722 for ; Sun, 4 Sep 2016 22:58:46 +0000 (UTC) Received: from mail-it0-f53.google.com (mail-it0-f53.google.com [209.85.214.53]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id C346EE9 for ; Sun, 4 Sep 2016 22:58:45 +0000 (UTC) Received: by mail-it0-f53.google.com with SMTP id c198so123286627ith.1 for ; Sun, 04 Sep 2016 15:58:45 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20160904001031.t7sv5isw5tc46pxr@thunk.org> References: <57C78BE9.30009@linaro.org> <20160902012531.GB28461@sasha-lappy> <20160902095417.GJ3950@sirena.org.uk> <1472827326.2519.14.camel@HansenPartnership.com> <20160904001031.t7sv5isw5tc46pxr@thunk.org> From: Amit Kucheria Date: Mon, 5 Sep 2016 04:28:44 +0530 Message-ID: To: "Theodore Ts'o" Content-Type: text/plain; charset=UTF-8 Cc: James Bottomley , "ltsi-dev@lists.linuxfoundation.org" , "ksummit-discuss@lists.linuxfoundation.org" , "gregkh@linuxfoundation.org" Subject: Re: [Ksummit-discuss] [Stable kernel] feature backporting collaboration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, Sep 4, 2016 at 5:40 AM, Theodore Ts'o wrote: > > If it reduces the number of massive features that have to be > backported to 4.4, it might be that pushing them to use 4.7 (or > waiting for the next LTS kernel, which should hopefully be coming soon > anyway) might be less risky and less work than trying to back port > feature patchsets to 4.4 or 3.18. OK, I'll bite. The vendors depend on Google providing an Android common tree[1] to build their BSP on top of. Currently, there isn't anything newer than a 4.4-based common tree from Google. It'll be early 2017 by the time 4.9 LTS is released and the Android common tree is available on it before vendors can even start porting their BSPs to it. Some are quicker than others, but safe to say that it'll be summer 2017 by the time the vendor BSPs can run on 4.9 LTS. That leaves very little time for product testing[2] and some slack, in order to ready devices for the Christmas market[3]. The project managers will flag that as a 'risk' and the vendor will stick to a 4.4 LTS. But since 4.4 LTS misses some key features that have landed in 4.5, 4.6, 4.7 and 4.8, something like LSK will fill that gap by backporting those features. So the problem is that it might be 2018 before the first 4.9-based CE devices hit the market. Now, if everything was on its way upstream, the BSP deltas would be smaller and the whole porting and validation exercise on top of the Android common tree would take much less time. But we aren't there yet for all vendors, some are doing better than others. Regards, Amit [1] https://android.googlesource.com/kernel/common/ [2] Across several SoC variants, I might add [3] This may not be uniformly important across the globe, but it is an empirical observation that flagship devices with the latest software tend to appear in the 2nd half of the year.