[OE-core] IMAGE_FEATURES vs EXTRA_IMAGE_FEATURES?

[Paul Eggleton]

On Friday 09 March 2012 08:38:25 Robert P. J. Day wrote:
>   again, reading the poky ref manual over at yocto, and here's the
> explanation of EXTRA_IMAGE_FEATURES:
> 
>   "Allows extra packages to be added to the generated images. You set
> this variable in the local.conf configuration file. Note that some
> image features are also added using the IMAGE_FEATURES variable
> generally configured in image recipes. You can use this variable to
> add more features in addition to those."
> 
>   now that *sounds* like you would just *assign* that in your
> local.conf file to add some features, as in:
> 
> EXTRA_IMAGE_FEATURES = "fubar snafu"
> 
> or something similar.
> 
>   but first, how is that different from:
> 
> IMAGE_FEATURES += "fubar snafu"
> 
> after all, bitbake.conf contains:
> 
> IMAGE_FEATURES += "${EXTRA_IMAGE_FEATURES}"

If the image recipe itself sets IMAGE_FEATURES with = instead of += then this 
will not work; but neither will setting EXTRA_IMAGE_FEATURES unless the recipe 
adds that as well. FWIW all of the recipes in OE-Core that set IMAGE_FEATURES 
add to it with +=.

I suspect it was just seen as a bit safer to have EXTRA_IMAGE_FEATURES as the 
variable you can do whatever you want with in local.conf.

>   also, i notice this in core-image-rt-sdk.bb:
> 
> IMAGE_FEATURES += "dev-pkgs tools-sdk"
> EXTRA_IMAGE_FEATURES += "tools-debug tools-profile tools-testapps
> debug-tweaks"
> 
> what is the point of those features being broken over those two
> variables?

Yes, that looks silly to me too. We should probably correct it. (Feel free to 
file a bug or submit a patch ;)

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre