Date: Mon, 11 Feb 2008 21:17:51 -0800
From: Arjan van de Ven <arjan@infradead.org>
To: Greg KH <greg@kroah.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
       LKML <linux-kernel@vger.kernel.org>, linux-next@vger.kernel.org,
       linux-arch@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       Linus <torvalds@linux-foundation.org>
Subject: Re: Announce: Linux-next (Or Andrew's dream  :-))
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In-Reply-To: <20080212044314.GA4888@kroah.com>
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	<20080212042133.GA4625@kroah.com>
	<20080211203146.3d28d1a0@laptopd505.fenrus.org>
	<20080212044314.GA4888@kroah.com>
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On Mon, 11 Feb 2008 20:43:14 -0800
Greg KH <greg@kroah.com> wrote:

> On Mon, Feb 11, 2008 at 08:31:46PM -0800, Arjan van de Ven wrote:
> > On Mon, 11 Feb 2008 20:21:33 -0800
> > Greg KH <greg@kroah.com> wrote:
> > 
> > 
> > > > The maintainer will be notified.  I hope to provide some clue
> > > > as to what the conflict is with, but probably not initially.
> > > > 
> > > > I will attempt to build the tree between each merge (and a
> > > > failed build will again cause the offending tree to be dropped).
> > > 
> > > This is going to get really interesting, especially when (not if)
> > > we do more global api changes.  Look at the last round of kobject
> > > changes. That touched a lot of different places, and other trees
> > > ended up not building because of it, because I changed apis and
> > > they had added new code based on the old apis.
> > > 
> > > I think the only way to fix this is not going to just "drop the
> > > tree" like you are suggesting, but to let both people know (the
> > > person who caused the change, and the person who's tree broke
> > > after the merge), and then either add a "fixup patch" for the
> > > build like Andrew has been doing, or disabling something from the
> > > build section.
> > > 
> > 
> > in my experience, the only chance you have is doing API changes as
> > first in the set of changes, and then hoping (making) all other
> > trees use the new APIs. Any other order just turns into an
> > impossible mismash.
> 
> I agree, and that's what I do.
> 
> The problem is, the API change is still in my tree.  So, if for
> example, the IB tree goes and adds some new functionality before my
> API changes have landed, they need to use the "old" API in order for
> them to be able to test and build things on their own.  Then, when
> the -next tree merges everything together, the IB tree breaks the
> build, not my driver tree.
> 
> It's those "who goes first" type things that end up being the cause
> of a lot of Andrew's headaches I think :)
> 

this is why you need specific trees for just the API change, and these
need to EXPLICITLY go first before EVERYTHING ELSE. Yes this needs a bit of coordination,
but it's the only way.
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