fs/iso9660: add support for grub2

After having extended the iso9660 support to allow isolinux as an
alternative to grub, this commit adds grub2 as a third
alternative. With the previous work done to support isolinux, adding
support for grub2 is fairly trivial.

[Thomas: set timeout to 10 seconds and not 5 seconds, in order to
match the configuration used for grub.]

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

fs/iso9660/Config.in

@@ -2,7 +2,9 @@ config BR2_TARGET_ROOTFS_ISO9660
 	bool "iso image"
 	depends on (BR2_i386 || BR2_x86_64)
 	depends on BR2_LINUX_KERNEL
-	depends on BR2_TARGET_GRUB || BR2_TARGET_SYSLINUX_ISOLINUX
+	depends on BR2_TARGET_GRUB || \
+		BR2_TARGET_GRUB2 || \
+		BR2_TARGET_SYSLINUX_ISOLINUX
 	select BR2_LINUX_KERNEL_INSTALL_TARGET \
 	       if (!BR2_TARGET_ROOTFS_ISO9660_INITRD && !BR2_TARGET_ROOTFS_INITRAMFS)
 	help
@@ -29,6 +31,15 @@ config BR2_TARGET_ROOTFS_ISO9660_GRUB
 	depends on BR2_TARGET_GRUB
 	select BR2_TARGET_GRUB_FS_ISO9660
 
+config BR2_TARGET_ROOTFS_ISO9660_GRUB2
+	bool "grub2"
+	depends on BR2_TARGET_GRUB2
+	help
+	  Use Grub 2 as the bootloader for the ISO9660 image. Make
+	  sure to enable the 'iso9660' module in
+	  BR2_TARGET_GRUB2_BUILTIN_MODULES and to use 'cd' as the boot
+	  partition in BR2_TARGET_GRUB2_BOOT_PARTITION=.
+
 config BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
 	bool "isolinux"
 	depends on BR2_TARGET_SYSLINUX_ISOLINUX
@@ -38,6 +49,7 @@ endchoice
 config BR2_TARGET_ROOTFS_ISO9660_BOOT_MENU
 	string "Boot menu.lst file"
 	default "fs/iso9660/menu.lst" if BR2_TARGET_ROOTFS_ISO9660_GRUB
+	default "fs/iso9660/grub.cfg" if BR2_TARGET_ROOTFS_ISO9660_GRUB2
 	default "fs/iso9660/isolinux.cfg" if BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
 	help
 	  Use this option to provide a custom bootloader configuration
@@ -69,7 +81,7 @@ config BR2_TARGET_ROOTFS_ISO9660_HYBRID
 
 endif
 
-comment "iso image needs a Linux kernel and one of grub or isolinux to be built"
+comment "iso image needs a Linux kernel and one of grub, grub2 or isolinux to be built"
 	depends on BR2_i386 || BR2_x86_64
 	depends on !BR2_LINUX_KERNEL || \
-		!(BR2_TARGET_GRUB || BR2_TARGET_SYSLINUX_ISOLINUX)
+		!(BR2_TARGET_GRUB || BR2_TARGET_GRUB2 || BR2_TARGET_SYSLINUX_ISOLINUX)

fs/iso9660/grub.cfg

@@ -0,0 +1,7 @@
+set default="0"
+set timeout="10"
+
+menuentry "Buildroot" {
+	linux __KERNEL_PATH__ root=/dev/sr0
+	initrd __INITRD_PATH__
+}

fs/iso9660/iso9660.mk

@@ -53,6 +53,15 @@ define ROOTFS_ISO9660_INSTALL_BOOTLOADER
 	$(INSTALL) -D -m 0644 $(GRUB_DIR)/stage2/stage2_eltorito \
 		$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/stage2_eltorito
 endef
+else ifeq ($(BR2_TARGET_ROOTFS_ISO9660_GRUB2),y)
+ROOTFS_ISO9660_DEPENDENCIES += grub2
+ROOTFS_ISO9660_BOOTLOADER_CONFIG_PATH = \
+	$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/grub.cfg
+ROOTFS_ISO9660_BOOT_IMAGE = boot/grub/grub-eltorito.img
+define ROOTFS_ISO9660_INSTALL_BOOTLOADER
+	$(INSTALL) -D -m 0644 $(BINARIES_DIR)/grub-eltorito.img \
+		$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/grub-eltorito.img
+endef
 else ifeq ($(BR2_TARGET_ROOTFS_ISO9660_ISOLINUX),y)
 ROOTFS_ISO9660_DEPENDENCIES += syslinux
 ROOTFS_ISO9660_BOOTLOADER_CONFIG_PATH = \