rpi-config: warn on config.txt exceeding 16k

The firmware has a size limit in handling config.txt depending the
hardware and it may prevent the hardware from booting if file exceeds
it.

That limit is not documented yet[1] but the links[2][3] mention about
16k.

This warns if the config.txt is larger than 16k.

[1]: https://www.raspberrypi.com/documentation/computers/config_txt.html
[2]: https://forums.raspberrypi.com/viewtopic.php?p=2159238
[3]: raspberrypi/firmware#1848

Signed-off-by: Gaël PORTAY <[email protected]>

Author: gportay

recipes-bsp/bootfiles/rpi-config_git.bb

@@ -341,6 +341,12 @@ do_deploy:append() {
     if grep -q -E '^.{80}.$' ${DEPLOYDIR}/${BOOTFILES_DIR_NAME}/config.txt; then
         bbwarn "config.txt contains lines longer than 80 characters, this is not supported"
     fi
+
+    # Warn about too big file!
+    size=$(stat -c '%s' $CONFIG)
+    if [ "$size" -gt 16384 ]; then
+        bbfatal "config.txt larger than 16k is not necessarily supported"
+    fi
 }
 do_deploy[vardeps] += "${RPI_CONFIG_STRIP}"