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
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