Re: Uses of Linux backports in the industry

[Pavel Machek <pavel@ucw.cz>]

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
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