[yocto] Board specific bbappend file

[Martin Jansa]

On Thu, Dec 05, 2013 at 11:51:18AM -0500, Bruce Ashfield wrote:
> On 13-12-05 11:44 AM, Stefan Roese wrote:
> > On 05.12.2013 17:33, Bruce Ashfield wrote:
> >>>> What exactly are you tried to change on a per-board basis ? Assuming
> >>>> it is variables, you can use the standard OVERRIDES mechanism to
> >>>> have a version specific bbappend, that changes variables on a per
> >>>> board basis.
> >>>>
> >>>> i.e.
> >>>>
> >>>>         FOO_<machine name> = "bar"
> >>>>         FOO_<another machine name> = "bar2"
> >>>>
> >>>> Assuming the generic recipe uses these variables appropriately, you'll
> >>>> be fine.
> >>>
> >>> Specifically its the SRC_URI / SRC_URI_append variable (e.g. for a linux
> >>> kernel and u-boot etc). And since this one is used in many recipes, I
> >>> can't just put those settings in the machine conf file.
> >>>
> >>> Do you have any recommendations how to change this variable (per recipe)
> >>> without touching the generic bb file?
> >>
> >> You can absolutely change the SRC_URI on a per-board basis. Just use
> >> the technique that I showed above, and do it in a bbappend to your
> >> linux recipe.
> >>
> >> i.e. something like: SRC_URI_qemux86 += "file://myfancypatch.patch"
> >
> > Yes, right. But this would mean doing it in a "generic" bbappend file? E.g.
> >
> 
> Definitions vary. I wouldn't call that generic :)
> 
> > recipe:
> > linux-xyz_3.12.bb
> >
> > and its "generic" append file:
> > linux-xyz_3.12.bbappend
> >
> > And thinking about for example 20 boards, this would mean to add 20
> > "SRC_URI_fooabc" defines to this bbappend file. Just shifting the
> > changes from the bb file to the "common" bbappend file.
> 
> Yes that's how variable namespace and override resolution works (at
> a high level).
> 
> >
> > What I was looking for is more a way to do this on a one-file-per-board
> > basis. Is this possible somehow?
> 
> There are plenty of things you could do, but I'd think of them more as
> hacks (or maybe someone else reading has a clean suggestion that I'm
> not aware of) with python, etc.
> 
> You could also have a layer per board, and each layer have a bbappend
> with the boards changes, that's what layers provide already.

Overrides should be used even in cases with separate layer for each
board.

Documentation was improved lately about this problem:
http://www.yoctoproject.org/docs/1.5/dev-manual/dev-manual.html#best-practices-to-follow-when-creating-layers

> On a separate note, if you really are managing this many boards, with
> patches, configs and separate changes you really don't want to spread
> those patches into many layers, files and rcipes. Maintenance becomes
> a big problem, as does patch failures and consistent configuration
> management.
> 
> Cheers,
> 
> Bruce
> 
> >
> > Thanks,
> > Stefan
> >
> 
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-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa at gmail.com
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