package/rpi-firmware: add option to use custom cmdline.txt

Currently, the cmdline.txt file is installed in $(BINARIES_DIR) by the
rpi-firmware package. Overriding files in there can not be done with an
overlay (which only applies to $(TARGET_DIR)), and thus requires using
either a post-build or post-image script, which is not always very
practical when a custom file must be used.

Like was done in 689b9ac439ab (package/rpi-firmware: rework boot/config
file handling) for config.txt, add an option to allow users to specify
the path to a custom cmdline.txt.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/rpi-firmware/Config.in

@@ -69,6 +69,13 @@ config BR2_PACKAGE_RPI_FIRMWARE_CONFIG_FILE
 	  Path to a file stored as config.txt in the boot partiton
 	  of the generated SD card image.
 
+config BR2_PACKAGE_RPI_FIRMWARE_CMDLINE_FILE
+	string "Path to a file stored as boot/cmdline.txt"
+	default "board/raspberrypi/cmdline.txt"  # legacy
+	help
+	  Path to a file stored as cmdline.txt in the boot partiton
+	  of the generated SD card image.
+
 config BR2_PACKAGE_RPI_FIRMWARE_INSTALL_DTBS
 	bool "Install Device Tree Blobs (DTBs)"
 	default y

package/rpi-firmware/rpi-firmware.mk

@@ -35,6 +35,14 @@ define RPI_FIRMWARE_INSTALL_CONFIG
 endef
 endif
 
+RPI_FIRMWARE_CMDLINE_FILE = $(call qstrip,$(BR2_PACKAGE_RPI_FIRMWARE_CMDLINE_FILE))
+ifneq ($(RPI_FIRMWARE_CMDLINE_FILE),)
+define RPI_FIRMWARE_INSTALL_CMDLINE
+	$(INSTALL) -D -m 0644 $(RPI_FIRMWARE_CMDLINE_FILE) \
+		$(BINARIES_DIR)/rpi-firmware/cmdline.txt
+endef
+endif
+
 ifeq ($(BR2_PACKAGE_RPI_FIRMWARE_INSTALL_DTBS),y)
 define RPI_FIRMWARE_INSTALL_DTB
 	$(foreach dtb,$(wildcard $(@D)/boot/*.dtb), \
@@ -79,9 +87,9 @@ endef
 endif # INSTALL_VCDBG
 
 define RPI_FIRMWARE_INSTALL_IMAGES_CMDS
-	$(INSTALL) -D -m 0644 package/rpi-firmware/cmdline.txt $(BINARIES_DIR)/rpi-firmware/cmdline.txt
 	$(RPI_FIRMWARE_INSTALL_BIN)
 	$(RPI_FIRMWARE_INSTALL_CONFIG)
+	$(RPI_FIRMWARE_INSTALL_CMDLINE)
 	$(RPI_FIRMWARE_INSTALL_DTB)
 	$(RPI_FIRMWARE_INSTALL_DTB_OVERLAYS)
 endef