Re: Uses of Linux backports in the industry

Pavel Machek
2015-06-23T18:50:11Z

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@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.). :-(

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...

Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html