Hi Robert,

On Wed, Mar 10, 2021 at 06:16:44AM -0500, Robert P. J. Day wrote:

On Tue, 9 Mar 2021, Quentin Schulz wrote:

Hi Robert,

On Tue, Mar 09, 2021 at 09:39:14AM -0500, Robert P. J. Day wrote:

bitbake manual, chapter 3, examples of conditional syntax:

https://docs.yoctoproject.org/bitbake/bitbake-user-manual/bitbake-user-manual-metadata.html#examples

correctly distinguishes between A_foo_append and A_append_foo, but how
often would one use that first form, anyway?

most uses of conditional appending are either just straight
appending:

VAR_append = "fubar"

or used with an override thusly:

VAR_append_x86 = "snafu"

is there an actual practical usage of, say:

VAR_x86_append = "huh"

i can't remember the last time i saw something of that form and,
while it might be worth explaining, it seems that the reader might be
warned that that form is almost certainly *not* what they want.

Yes, in 99% of the cases, you want VAR_append_foo and not VAR_foo_append.

VAR_foo_append makes sense when you want to append to VAR_foo which
is a way to override completely VAR for builds matching the foo
override. This happens in kernel-yocto recipes where branches and
defconfigs are different per machine for example.

can you point at an actual example of that? i took a look and all
the yocto kernel recipes i see use the first form. am i just looking
in the wrong place?

https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/recipes-kernel/linux/linux-yocto_5.10.bb#n12
for example.

This is an example of a "valid" use case (not that there are invalid
ones) for VAR_foo.

Would probably a better example:
https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/recipes-kernel/linux/linux-yocto_5.10.bb#n50

So, you might decide that a machine is so much different than others
that KERNEL_FEATURES should be overridden for said machine.

Then in a bbappend, one might want to add another feature for this
machine, they'll therefore need to use KERNEL_FEATURES_foo_append.

I do not have examples at hand of VAR_foo_append except the ones Leon
sent in another mail. Which should show how rare it is :)

Cheers,
Quentin