From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vms173015pub.verizon.net ([206.46.173.15]) by linuxtogo.org with esmtp (Exim 4.72) (envelope-from ) id 1SCyAM-0000Hm-LS for openembedded-core@lists.openembedded.org; Wed, 28 Mar 2012 21:04:18 +0200 Received: from gandalf.denix.org ([unknown] [71.178.225.66]) by vms173015.mailsrvcs.net (Sun Java(tm) System Messaging Server 7u2-7.02 32bit (built Apr 16 2009)) with ESMTPA id <0M1L00C5HZ7N3K53@vms173015.mailsrvcs.net> for openembedded-core@lists.openembedded.org; Wed, 28 Mar 2012 13:54:59 -0500 (CDT) Received: by gandalf.denix.org (Postfix, from userid 1000) id DB38F20264; Wed, 28 Mar 2012 14:54:58 -0400 (EDT) Date: Wed, 28 Mar 2012 14:54:58 -0400 From: Denys Dmytriyenko To: Patches and discussions about the oe-core layer Message-id: <20120328185458.GB32193@denix.org> References: <1332524132-24689-1-git-send-email-trini@ti.com> <1332753313.28414.91.camel@ted> <20120326162531.GD21518@bill-the-cat> <1332780976.28414.130.camel@ted> MIME-version: 1.0 In-reply-to: <1332780976.28414.130.camel@ted> User-Agent: Mutt/1.5.20 (2009-06-14) Subject: Re: [PATCH] qemu.inc: Use '=' for IMAGE_FSTYPES X-BeenThere: openembedded-core@lists.openembedded.org X-Mailman-Version: 2.1.11 Precedence: list Reply-To: Patches and discussions about the oe-core layer List-Id: Patches and discussions about the oe-core layer List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Mar 2012 19:04:18 -0000 Content-type: text/plain; charset=us-ascii Content-disposition: inline On Mon, Mar 26, 2012 at 05:56:16PM +0100, Richard Purdie wrote: > 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 > > > > --- > > > > 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? Richard, So, what is the subtle difference between += that we started with and =+ that you recommended at the end? I realize those are for append and prepend, but are they handled any different? Was your recommendation to use =+ at the end, instead of += that was used originally, based on some specifics? Thanks. -- Denys