[OE-core] Consistency and use cases for IMAGE_FSTYPES

[Darren Hart]

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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?

IMAGE_FSTYPES_append_machine = "Z" ?

or

IMAGE_EXTRA_FSTYPES = "Z"

- -- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel
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