[PATCH 1/4] per-kernel.bbclass: add class

["chris.larson via isar-users" <isar-users@googlegroups.com>]

From: Christopher Larson <chris.larson@siemens.com>

Add support for generation of per-kernel recipe variants. This aids in the
ability for a MACHINE to support multiple kernels, by allowing us to generate
per-kernel packages in recipes like external kernel modules.

A new variable KERNEL_NAMES will list the kernels for which variants will be
generated. For any kernels listed other than KERNEL_NAME, a variant of the
recipe will be produced, to generate a package or packages for that kernel.
In each variant, the KERNEL_NAME variable will be set to the kernel name for
which the variant is being built, and the `kernel-<kernel_name>` override
will be added, allowing for further metadata customization on a per-kernel
basis.

Signed-off-by: Christopher Larson <chris.larson@siemens.com>
---
 meta/classes/per-kernel.bbclass | 35 +++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 meta/classes/per-kernel.bbclass

diff --git a/meta/classes/per-kernel.bbclass b/meta/classes/per-kernel.bbclass
new file mode 100644
index 00000000..8abe117f
--- /dev/null
+++ b/meta/classes/per-kernel.bbclass
@@ -0,0 +1,35 @@
+# Generate per-kernel recipe variants
+#
+# Recipes which are specific to a specific kernel currently append KERNEL_NAME to the PN,
+# and depend on and target that specific kernel. For a machine which supports and builds
+# multiple kernel images, there is a need to generate a variant of the recipe for each
+# kernel image.
+# 
+# Each variant listed in KERNEL_NAMES will add `kernel-<kernel_name>` to the OVERRIDES variable, and
+# `per-kernel:<kernel_name>` to the BBCLASSEXTEND variable. In addition, KERNEL_NAME will be
+# set to the kernel name for the current variant.
+#
+# Copyright (c) Siemens AG, 2025
+# SPDX-License-Identifier: MIT
+
+OVERRIDES .= ":kernel-${KERNEL_NAME}"
+
+KERNEL_NAMES ?= "${KERNEL_NAME}"
+BBCLASSEXTEND += "${@' '.join(f'per-kernel:{kernel}' for kernel in d.getVar('KERNEL_NAMES').split() if kernel != d.getVar('KERNEL_NAME'))}"
+
+python per_kernel_virtclass_handler() {
+    orig_pn = d.getVar('PN')
+
+    d = e.data
+    extend = d.getVar('BBEXTENDCURR') or ''
+    variant = d.getVar('BBEXTENDVARIANT') or ''
+    if extend != 'per-kernel':
+        return
+    elif variant == '':
+        d.appendVar('PROVIDES', f' {orig_pn}')
+        return
+
+    d.setVar('KERNEL_NAME', variant)
+}
+addhandler per_kernel_virtclass_handler
+per_kernel_virtclass_handler[eventmask] = "bb.event.RecipePreFinalise"
-- 
2.47.2

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