[OE-core] Consistency and use cases for IMAGE_FSTYPES

[Tom Rini]

On Fri, Mar 23, 2012 at 09:34:02AM -0700, Darren Hart wrote:
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> 
> On 03/23/2012 09:29 AM, Tom Rini wrote:
> > On Fri, Mar 23, 2012 at 09:17:20AM -0700, Darren Hart wrote:
> >> On 03/23/2012 08:48 AM, Tom Rini wrote:
> >>> On Fri, Mar 23, 2012 at 01:14:24AM +0000, Richard Purdie
> >>> wrote:
> >>>> 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).
> >>> 
> >>> Well, one problem that would make this a bugfix is that no one
> >>> does what you say we agreed on today.  oe-core has qemu.inc
> >>> using ?=, meta-intel is using += and meta-ti is mixed (which is
> >>> what got this started).
> >>> 
> >>> 
> >> 
> >> Is this causing any nasty failures right now, or is it in the
> >> "this is a confusing mess and it would be nice to get it cleaned
> >> up" bucket? If the latter, I think I'd prefer to wait a bit an
> >> clean up the local.conf/machine.conf IMAGE_FSTYPES clobbering
> >> issue.
> > 
> > Well, I found this as part of adding UBI support for a board and
> > it wasn't sticking.
> > 
> > I'd go so far as to say that for a release, we really need to pick
> > a standard, document and follow it.  If it's machine.conf does =,
> > everyone else does += and user's have to do _local =, fine, it
> > sucks but it's documented and consistent on all of the BSP layers.
> > 
> >> If this isn't really fixable (for whatever requirements bitbake
> >> has on load/parse order of config files), then Koen's
> >> EXTRA_IMAGE_FSTYPES seems like the most consistent mechanism with
> >> other things, like CORE_IMAGE_EXTRA_INSTALL (OK, maybe
> >> IMAGE_EXTRA_FSTYPES ?).
> >> 
> >> So the default becomes:
> >> 
> >> IMAGE_FSTYPES ?= ${IMAGE_EXTRA_FSTYPES}
> >> 
> >> and DISTROs might define that as:
> >> 
> >> IMAGE_FSTYPES += "yyy"
> >> 
> >> and users can update local.conf to be:
> >> 
> >> IMAGE_FSTYPES = "X"
> >> 
> >> But, doesn't this meant the DISTRO append will still change the 
> >> IMAGE_FSTYPES to "X yyy" even though the user intended "only X"?
> > 
> > How about: bitbake.conf: IMAGE_FSTYPES ??= ${IMAGE_EXTRA_FSTYPES} 
> > distro.conf: IMAGE_FSTYPES ?= "yyy ${IMAGE_EXTRA_FSTYPES}" 
> > local.conf: IMAGE_FSTYPES = "X"
> > 
> > Or am I forgetting the magic of ??= again...
> > 
> 
> What would machine.conf do in this scenario?

OK, lets test things out.  bitbake.conf, distro.conf set as above (with
machine.conf providing IMAGE_EXTRA_FSTYPES).  

> IMAGE_FSTYPES_append_machine = "Z" ?

With this in local.conf, IMAGE_FSTYPES = "distro machineZ" (the fun of
_append semantics, you would have wanted " Z").

> IMAGE_EXTRA_FSTYPES = "Z"

Again in local.conf, this is ignored and it's the original problem.
Making this IMAGE_EXTRA_FSTYPES_local = "Z" is also ignored because
local overrides were removed in 83ce96f (really? ok..).  Making this
IMAGE_EXTRA_FSTYPES_forcevariable = "Z" yields IMAGE_FSTYPES = "distro Z".

-- 
Tom
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