[OE-core] Consistency and use cases for IMAGE_FSTYPES

[Richard Purdie]

On Thu, 2012-03-22 at 19:53 -0400, Denys Dmytriyenko wrote:
> On Thu, Mar 22, 2012 at 11:26:24PM +0000, Richard Purdie wrote:
> > On Fri, 2012-03-09 at 14:39 -0700, Tom Rini wrote:
> > > Hey all,
> > > 
> > > Over in meta-ti I kicked off a discussion
> > > (https://lists.yoctoproject.org/pipermail/meta-ti/2012-March/000779.html)
> > > about if we should be using '?=' or '+=' with IMAGE_FSTYPES in the
> > > machine conf files.  This has been discussed a little bit before
> > > (http://thread.gmane.org/gmane.comp.handhelds.openembedded.core/2060/focus=2061).
> > >  The problem is we have the following and I believe ultimately
> > > conflicting use cases:
> > 
> > I've been under the impression that we decided upon:
> > 
> > > - The machine needs to say 'I need or support the following formats'
> > 
> > so the machine starts and sets:
> > 
> > IMAGE_FSTYPES = "xxxx"
> > 
> > > - The distro needs to say 'I always want format X'
> > 
> > so the distro can do:
> > 
> > IMAGE_FSTYPES += " yyy"
> > 
> > > - The user needs to say 'I know best, give me only format X'
> > 
> > So the user can do:
> > 
> > IMAGE_FSTYPES = "X"
>
> Since local.conf gets parsed before machine.conf and distro.conf, the user 
> needs to do this override:
> 
> IMAGE_FSTYPES_local = "X"
> 
> Otherwise machine.conf will always overwrite it with "xxxx" with its 
> unconditional assignment.

Right, I'd forgotten that little detail :/.

It actually makes me wonder if our include order is the right one but
now isn't the time to try changing that.

I agree the neatest way to change it is probably something like
MACHINE_FSTYPES. I do worry a lot about backwards compatibility though
and I'd also point out where we're at in the release cycle (bug fix
only).

Cheers,

Richard