meta-riscv: add deprecation warning function, message

Add classes/warn-deprecated-machines.bbclass with a Python function,
then INHERIT it in conf/layer.conf.

Start with deprecating the following MACHINEs:

- beaglev
- visionfive

These will be removed with the Yocto 6.1 release.

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

classes/warn-deprecated-machines.bbclass

@@ -0,0 +1,21 @@
+# Print a warning when a build is started with a MACHINE which is slated to be
+# removed as of a future Yocto Project release.
+
+python warn_deprecated_machines() {
+    deprecated_machines = {
+        "beaglev-starlight-jh7100": "Yocto 6.1",
+        "visionfive": "Yocto 6.1",
+    }
+
+    machine = d.getVar("MACHINE")
+
+    if machine in deprecated_machines:
+        removal_release = deprecated_machines[machine]
+        bb.warn(
+            f"MACHINE='{machine}' is deprecated and will no longer be supported "
+            f"after {removal_release}. Please consider an alternative BSP."
+        )
+}
+
+addhandler warn_deprecated_machines
+warn_deprecated_machines[eventmask] = "bb.event.BuildStarted"

conf/layer.conf

@@ -157,3 +157,6 @@ COMPATIBLE_HOST:pn-samba:riscv32 = "null"
 COMPATIBLE_HOST:pn-smbnetfs:riscv32 = "null"
 COMPATIBLE_HOST:pn-gnome-control-center:riscv32 = "null"
 COMPATIBLE_HOST:pn-thunar-shares-plugin:riscv32 = "null"
+
+# Use our deprecation warning function
+INHERIT += "warn-deprecated-machines"