[OE-core] IMAGE_FEATURES vs EXTRA_IMAGE_FEATURES?

[Robert P. J. Day]

  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}"

  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?  and wouldn't that cause trouble if someone starts with a
base of core-image-rt-sdk, then *assigns* to EXTRA_IMAGE_FEATURES in
their local.conf, would that not override that setting in the .bb
file?  isn't that a bit confusing?

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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