Re: Uses of Linux backports in the industry

From: Pavel Machek
Date: Tue Jun 23 2015 - 14:50:13 EST

On Fri 2015-05-29 13:36:09, Theodore Ts'o wrote:
> 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@xxxxxxxx> 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.). :-(

Actually, what we really want is chip vendors to clean up the
interfaces, and merge their changes upstream... Perhaps we'll be able
to install normal distros on cellphones one day...

(cesky, pictures)
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