On Mon, 2012-03-26 at 09:25 -0700, Tom Rini wrote: > On Mon, Mar 26, 2012 at 10:15:13AM +0100, Richard Purdie wrote: > > On Fri, 2012-03-23 at 10:35 -0700, Tom Rini wrote: > > > As per > > > http://lists.linuxtogo.org/pipermail/openembedded-core/2012-March/019772.html > > > a machine conf file should use '=' to set IMAGE_FSTYPES. > > > > > > Signed-off-by: Tom Rini <[email protected]> > > > --- > > > meta/conf/machine/include/qemu.inc | 2 +- > > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > As someone pointed out, what I mentioned in that email sadly doesn't > > work although it would be nice if they did. I suspect this is why we're > > using += since: > > We aren't using += today. We (openembedded-core) use ?=. meta-intel > uses += and meta-ti is mixed (and I don't have meta-fsl-* handy). > > > > - The machine needs to say 'I need or support the following formats' > > > > so the machine ensures those formats exist at a minimum: > > > > 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' > > > > This one is the problem case so the user has to use overrides: > > > > IMAGE_FSTYPES_override = "X" > > > > (where override can be MACHINE or forcevariable) > > > > > - The user needs to say 'I know best, give me what you support + X' > > > > IMAGE_FSTYPES += " X" > > > > > > Whilst I think that is less than ideal since it forces use of overrides > > in local.conf to override, changing the += in machine conf files doesn't > > gain us much, it just breaks += in local.conf. > > > > I'm open to other feedback though... > > Well, I suggested ??= / ?= and posted some results from bitbake -e...
Ok. += plays out as above. I realise its not what is in qemu.inc, it is used in meta-intel though which I looked at after qemu.inc and I guess has confused me. With ?= in machine.conf: The user defined IMAGE_FSTYPES would override the machine ones. Distro can still append to it. The downside is a user append would not work out as expected. So the question is which is the more user expected behaviour? =+ makes overwriting IMAGE_FSTYPES hard ?= makes appending IMAGE_FSTYPES hard I suspect a user is more likely to want to append than overwrite. Getting an append to work with ?= is extremely non-obvious, even worse syntax than the =+ overwriting case with overrides. So bottom line, I'm tempted to recommend we use =+. Further thoughts? Cheers, Richard _______________________________________________ Openembedded-core mailing list [email protected] http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core
