Re: [PATCH] qemu.inc: Use '=' for IMAGE_FSTYPES

[Richard Purdie <richard.purdie@linuxfoundation.org>]

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 <trini@ti.com>
> ---
>  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:

> - 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...

Cheers,

Richard