Messages in this thread | | | Date | Fri, 29 May 2015 13:36:09 -0400 | From | Theodore Ts'o <> | Subject | Re: Uses of Linux backports in the industry |
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On Fri, May 29, 2015 at 05:01:00PM +0200, Richard Weinberger wrote: > On Fri, May 29, 2015 at 4:53 PM, Enrico Weigelt, metux IT consult > <weigelt@melag.de> wrote: > > Am 29.05.2015 um 04:54 schrieb Luis R. Rodriguez: > > Actually, I really wonder why folks are sticking to ancient kernels on > > newer hardware. > > Enterprise distribution kernels. Or "special" kernels like PREEMPT_RT. > Sometimes the vendor BSP is that horrid that a customer cannot afford > to forward port it > but wants recent stuff. So you need to backport...
Yep. The technique I used for the backporting ext4 encryption into the 3.10 android-common git tree in AOSP was to drop in the 3.18 versions of fs/ext4 and fs/jbd2 into the 3.10 tree (along with the associaed include files in include/linux and include/trace/events, of course), and then fix things up until they built correctly (using cherry-picks and in some cases, reverting some changes in the 3.18 version of fs/ext4). After I was sure the transplant of the 3.18 version of ext4 had "taken" correctly, with no test regressions, only then did I cherry-pick all of the ext4 encryption changes on top of 3.10.
The backport of ext4 encryption to the 3.18 version of android-common should be much easier. :-) Unfortunately, I also have to do a backport to the 3.14 android-common branch as well. <sigh>
Yes, it's ugly, but there still are some SOC and drivers that aren't available on newer kernels. Basically, the handset vendors need to lean a lot harder on the SOC and other peripheral (cell radios, GPS, etc., etc.). :-(
- Ted
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