On Friday, January 07, 2011 21:13:31 Devin Heitmueller wrote:
> On Fri, Jan 7, 2011 at 2:53 PM, Oliver Endriss <o.endr...@gmx.de> wrote:
> > Hi guys,
> >
> > are you aware that there is a lot of '#if 0' code in the HG repositories
> > which is not in GIT?
> >
> > When drivers were submitted to the kernel from HG, the '#if 0' stuff was
> > stripped, unless it was marked as 'keep'...
> >
> > This was fine, when development was done with HG.
> >
> > As GIT is being used now, that code will be lost, as soon as the HG
> > repositories have been removed...
> >
> > Any opinions how this should be handled?
> >
> > CU
> > Oliver
> I complained about this months ago.  The problem is that when we were
> using HG, the HG repo was a complete superset of what went into Git
> (including development/debug code).  But now that we use Git, neither
> is a superset of the other.
> If you base your changes on Git, you have to add back in all the
> portability code (and any "#if 0" you added as the maintainer for
> development/debugging).  Oh, and regular users cannot test any of your
> changes because they aren't willing to upgrade their entire kernel.
> If you base your changes on Hg, nothing merges cleanly when submitted
> upstream so your patches get rejected.
> Want to know why we are seeing regressions all over the place?
> Because *NOBODY* is testing the code until after the kernel goes
> stable (since while many are willing to install a v4l-dvb tree, very
> few will are willing to upgrade their entire kernel just to test one
> driver).  We've probably lost about 98% of our user base of testers.

Have you tried Mauro's media_build tree? I had to use it today to test a
driver from git on a 2.6.35 kernel. Works quite nicely. Perhaps we should
promote this more. I could add backwards compatibility builds to my daily
build script that uses this in order to check for which kernel versions
this compiles if there is sufficient interest.

> Oh, and users have to git clone 500M+ of data, and not everybody in
> the world has bandwidth fast enough to make that worth their time (it
> took me several hours last time I did it).

Currently the media_build tree copies the drivers from a git tree. Which, as
you say, can be a big problem for non-developers. But all it really needs are
the media drivers. So perhaps it might be a good idea to make a daily snapshot
of the drivers and make it available for download on linuxtv.org. That archive
is only 3.5 MB, so much easier to download.

> Anyway, I've beaten this horse to death and it's fallen on deaf ears.
> Merge overhead has reached the point where it's just not worth my
> time/effort to submit anything upstream anymore.

The hg tree is dead. Douglas Landgraf tried to maintain it, but it's just too
much work. Any attempt to work from the hg tree is doomed. The media_build
seems to be a viable alternative. As a developer you still have to go through
the painful process of cloning the git repo, but it is a one time thing. Once
it's cloned then you only have to follow the new commits, which is much, much

And regarding regressions: I'm amazed how few regressions we have considering
the furious rate of development. The media subsystem is still one of the most
active subsystems in the kernel and probably will remain so for the forseeable
future as well.

It would be a shame not to submit patches upstream, that never ends well in
the long run.

With respect to '#if 0': for the most part I'd say: good riddance. In my
many years of experience as a SW engineer I have never seen anyone actually
turn on '#if 0' code once it's been in the code for more than, say, a year.
Usually people just leave it there because they are too lazy to remove it,
or they don't understand what it is for and are too scared to remove it.

If it is code partially implementing a feature that needs more work, then
it may sound like a good idea to keep it. However, after it's in the code for
more than a year, then nobody remembers what the code was about and what still
had to be done to make it work. And it's hell to figure that out after such a
long time. Never put such code in the mainline. Keep it in a branch if you
have to.

Anyway, if there is some '#if 0' code that you want to preserve in git, then
you have to make a patch to add it. But you probably will have to have very
good reasons for adding '#if 0' code to the mainline.


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