Re: [linux-pm] suspend blockers & Android integration

[Thomas Gleixner <tglx@linutronix.de>]

James,

On Sun, 6 Jun 2010, James Bottomley wrote:

> On Sun, 2010-06-06 at 17:46 +0200, Thomas Gleixner wrote:
> > On Sun, 6 Jun 2010, James Bottomley wrote:
> > >
> > >      3. We've lost sight of one of the original goals, which was to
> > >         bring the android tree close enough to the kernel so that the
> > >         android downstream driver and board producers don't have to
> > >         choose between the android kernel and vanilla kernel.
> > 
> > There are two ways to do that w/o creating a dependcy on anything.
> > 
> > 1) merge the drivers w/o the suspend_blockers. It's not rocket science
> >    to have a patch which brings them back for android.
> 
> Well, we sort of tried this when Greg pulled some of them into the
> staging tree.  The problem is that without the annotations, the drivers
> are still different, and patches won't apply, so, unsurprisingly, they
> didn't get improved or even maintained.
> 
> > 2) merge the drivers with empty stub implementations for annotation.
> >    android just has to patch in the real one.
> 
> That's also possible.  This time, we would have a cosmetically closer
> tree ... however, what's in the kernel wouldn't be compilable for
> android ... which is where all the downstream wants to test, so they'd
> still be building for the android tree ... we just might have an easier
> time of it picking up their fixes.

The downstream users will be bound to the android tree anyway until
the full set of drivers for a given platform is completely merged. So
optimistically that would be 2.6.36, which gives us a couple of
months to sort out the whole thing.

Once a driver is merged mainline and the android tree switched over to
use the mainline version, fixes can be sent both ways and that's not a
real problem.

> > While I'd prefer #1, I' not in the way of #2.
> 
> I think 1 is unviable ... I'm not opposed to 2 but I'd like to try to
> get the kernel really closer to android before we go for the cosmetic
> only option.
> 
> > Both ways can get the drivers into the kernel and it could/should have
> > been done right from the beginning, but now we face a situation where
> > drivers are held hostage.
> > 
> > Then we can sit down more relaxed and fix the stuff in a way which
> > makes both sides happy. If we manage to replace them, we can deprecate
> > the stub implementation and remove it after a grace period. If we
> > rename them it's not an issue either. We can rename them right away to
> > a qos interface, but that does not really make a difference.
> > 
> > What we really want to avoid is implementing an user space contract in
> > a frenzy which binds us forever.
> 
> Well, that's why the QoS proposal ... it already has a userspace API ...
> we'd just be extending it for statistics, which looks like a wothwhile
> goal independent of android anyway.

Right, but there is no dependency for the driver merge on that.
 
> > It's not the suspend_blockers which are the causing the nightmare,
> > it's solely the drivers itself especially when there are different
> > implementations in both trees. And frankly, the drivers in android are
> > not in a shape which makes them flood in within 2 weeks. That's
> > serious work to get them brushed up and polished. So that gives us
> > quite a period of time to solve the suspend problem.
> 
> Right, so the sooner we make it easier for the drivers to use the kernel
> as their main repository, the better.

Yep, the fastest way is to provide two stub inlines in pm.h and let
the driver flood come in.

I think all of us involved in that can do with a break, where we sit
back, calm down and rethink w/o time pressure.

Thanks,

	tglx