Re: Using OVERRIDES to set variables from outside the recipe file


Robert P. J. Day
 

On Thu, 3 Dec 2020, Quentin Schulz wrote:

Hi Andrew,

On Thu, Dec 03, 2020 at 03:45:41AM +0000, Andrew Loader wrote:
In the bitbake user manual it has an example of how to set the variable value using the OVERRIDE variable

OVERRIDES = "architecture:os:machine"
TEST = "default"
TEST_os = "osspecific"
TEST_nooverride = "othercondvalue"

Lets say this is in the recipe called "test_0.1.bb" and we remove the OVERRIDES line from it

If we want to the OVERRIDES value to configure the recipe externally say in local.conf as I do not want to change the recipe how would I do that?
OVERRIDES is set in configuration files usually (always?). It can be
either in a distro if you use DISTROOVERRIDES, in a machine if you
use MACHINEOVERRIDES, and you might be able to add manually to it
from local.conf or other ways but I think you should go with
DISTROOVERRIDES or MACHINEOVERRIDES.

Then, the OVERRIDES (which contains MACHINEOVERRIDES:DISTROOVERRIDES
among other things) will be used in all recipes you can find and it
should just work.

You can use bitbake -e my-recipe | grep -e "^OVERRIDES=" to check
the content of the OVERRIDES variable. Note that righmost "OVERRIDE"
is the one which takes precedence over all others.
i'm going to weigh in on this, as it *seems* that andrew has the
same misunderstanding i had when, lo those many years ago, i read that
section in the BB manual, and read this:

OVERRIDES = "architecture:os:machine"
TEST = "default"
TEST_os = "osspecific"
TEST_nooverride = "othercondvalue"

my initial problem with that section was that it wasn't clear that
entities like "architecture" and "os" and so on were *replaceable*, in
that one was supposed to put *examples* of those values in those
places. (laugh if you like, but if one is totally new to overrides,
that section can be misinterpreted in a truly tragic way on first
reading.)

i recall extending that section to attempt to make it more
understandable, but i think, over the holidays, i'm going to rewrite
it again with a simpler introduction and more examples straight from
the code base. (i believe i was the one who added the example
involving overriding the value of KBRANCH based on the target arch.)

in any event, i can easily see a much longer and involved
introduction to overrides.

rday

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