Re: [OE-core][PATCH v5 1/5] kernel-module-split.bbclass: add get_ext_mod function for module signing

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Tue, 2026-08-25 at 22:49 +0200, Anis Bougrine wrote:
> Fixes [YOCTO #12927]
> 
> Out-of-tree module Makefiles invoke the kernel Makefile by appending
> the M= (the module directory) variable to the MAKEFLAGS.
> However, they usually do not provide a modules_sign target. Therefore,
> the kernel modules_sign target has to be invoked manually after retrieving
> M= variable from package source code Makefile.
> 
> This function retrieves the M= variable from an external module Makefile.
> 
> Reported-by: Ross Burton <ross.burton@arm.com>
> Signed-off-by: Anis Bougrine <anis.bougrine10@gmail.com>
> ---
>  .../kernel-module-split.bbclass               | 21 +++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/meta/classes-recipe/kernel-module-split.bbclass b/meta/classes-recipe/kernel-module-split.bbclass
> index ab2f0d1c37..bde7cd02dd 100644
> --- a/meta/classes-recipe/kernel-module-split.bbclass
> +++ b/meta/classes-recipe/kernel-module-split.bbclass
> @@ -42,6 +42,27 @@ KERNEL_MODULE_PACKAGE_PREFIX ?= ""
>  KERNEL_MODULE_PACKAGE_SUFFIX ?= "-${KERNEL_VERSION}"
>  KERNEL_MODULE_PROVIDE_VIRTUAL ?= "1"
>  
> +def get_ext_mod(d):
> +    """
> +    Extract the resolved Kbuild M= variable from an out of tree module Makefile variable database.
> +    """
> +    import re
> +    import bb.process
> +
> +    try:
> +        output = bb.process.run(
> +            "make -C %s --dry-run --print-data-base" % d.getVar("B")
> +        )[0]
> +    except bb.process.ExecutionError:
> +        return d.getVar("S")
> +
> +    for line in output.splitlines():
> +        m = re.match(r'^M\s*=\s*(.*)$', line)
> +        if m:
> +            return m.group(1).strip()
> +
> +    return d.getVar("S")
> +
>  python split_kernel_module_packages () {
>      import re
> 

Sorry, a couple of more things. I'm not sure if it helps but there is a
scripts/makefile-getvar which may be a simpler way to do this? It was
created for this kind of usage.

Also, we're aiming to move python functions into meta/lib/oe, probably
kernel.py in this case so new functions should really go in there.

Cheers,

Richard