Create menu entry to select device creation method

Four methods for the creation of device files in /dev are now
proposed:

 - static method uses device table as before
 - devtmpfs method enables this feature in kernel
 - mdev method adds mdev starting script to the file system
    and selects mdev itself for installation
 - udev method selects udev for installation

All dynamic methods are based on devtmpfs, so one doesn't need to care
about /dev folder.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

fs/Config.in

@@ -15,8 +15,29 @@ config BR2_ROOTFS_POST_BUILD_SCRIPT
 	  only argument. Make sure the exit code of that script is 0,
 	  otherwise make will stop after calling it.
 
+choice
+	prompt "/dev management"
+	default BR2_ROOTFS_DEVICE_CREATION_STATIC
+
+config BR2_ROOTFS_DEVICE_CREATION_STATIC
+	bool "Static using device table"
+
+config BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS
+	bool "Dynamic using devtmpfs only"
+
+config BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV
+	bool "Dynamic using mdev"
+	select BR2_PACKAGE_BUSYBOX
+
+config BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_UDEV
+	bool "Dynamic using udev"
+	select BR2_PACKAGE_UDEV
+
+endchoice
+
 config BR2_ROOTFS_DEVICE_TABLE
 	string "Path to the device table"
+	depends on BR2_ROOTFS_DEVICE_CREATION_STATIC
 	default "target/generic/device_table.txt"
 	help
 	  Specify the location of a device table, that will be passed

linux/linux.mk

@@ -133,6 +133,13 @@ ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
 	$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config)
 	$(call KCONFIG_DISABLE_OPT,CONFIG_INITRAMFS_COMPRESSION_NONE,$(@D)/.config)
 	$(call KCONFIG_ENABLE_OPT,CONFIG_INITRAMFS_COMPRESSION_GZIP,$(@D)/.config)
+endif
+ifneq ($(BR2_ROOTFS_DEVICE_CREATION_STATIC),y)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS,$(@D)/.config)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS_MOUNT,$(@D)/.config)
+endif
+ifeq ($(BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV),y)
+	$(call KCONFIG_SET_OPT,CONFIG_UEVENT_HELPER_PATH,\"/sbin/mdev\",$(@D)/.config)
 endif
 	$(TARGET_MAKE_ENV) $(MAKE) $(LINUX26_MAKE_FLAGS) -C $(@D) oldconfig
 	$(Q)touch $@

package/busybox/S10mdev

@@ -0,0 +1,20 @@
+#!/bin/sh
+#
+# Start mdev....
+#
+
+case "$1" in
+  start)
+	echo "Starting mdev..."
+	/sbin/mdev -s
+	;;
+  stop)
+	;;
+  restart|reload)
+	;;
+  *)
+	echo $"Usage: $0 {start|stop|restart}"
+	exit 1
+esac
+
+exit $?

package/busybox/busybox.mk

@@ -28,6 +28,19 @@ ifndef BUSYBOX_CONFIG_FILE
 	BUSYBOX_CONFIG_FILE = $(call qstrip,$(BR2_PACKAGE_BUSYBOX_CONFIG))
 endif
 
+# If mdev will be used for device creation enable it and copy S10mdev to /etc/init.d
+ifeq ($(BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV),y)
+define BUSYBOX_INSTALL_MDEV_SCRIPT
+	install -m 0755 package/busybox/S10mdev $(TARGET_DIR)/etc/init.d
+endef
+define BUSYBOX_SET_MDEV
+	$(call KCONFIG_ENABLE_OPT,CONFIG_MDEV,$(BUSYBOX_BUILD_CONFIG))
+	$(call KCONFIG_ENABLE_OPT,CONFIG_FEATURE_MDEV_CONF,$(BUSYBOX_BUILD_CONFIG))
+	$(call KCONFIG_ENABLE_OPT,CONFIG_FEATURE_MDEV_EXEC,$(BUSYBOX_BUILD_CONFIG))
+	$(call KCONFIG_ENABLE_OPT,CONFIG_FEATURE_MDEV_LOAD_FIRMWARE,$(BUSYBOX_BUILD_CONFIG))
+endef
+endif
+
 # If we have external syslogd, force busybox to use it
 ifeq ($(BR2_PACKAGE_SYSKLOGD),y)
 define BUSYBOX_SET_SYSKLOGD
@@ -122,6 +135,7 @@ define BUSYBOX_CONFIGURE_CMDS
 	$(BUSYBOX_SET_IPV6)
 	$(BUSYBOX_SET_RPC)
 	$(BUSYBOX_PREFER_STATIC)
+	$(BUSYBOX_SET_MDEV)
 	$(BUSYBOX_NETKITBASE)
 	$(BUSYBOX_NETKITTELNET)
 	@yes "" | $(MAKE) ARCH=$(KERNEL_ARCH) CROSS_COMPILE="$(TARGET_CROSS)" \
@@ -138,6 +152,7 @@ define BUSYBOX_INSTALL_TARGET_CMDS
 		$(INSTALL) -m 0755 -D package/busybox/udhcpc.script \
 			$(TARGET_DIR)/usr/share/udhcpc/default.script; \
 	fi
+	$(BUSYBOX_INSTALL_MDEV_SCRIPT)
 endef
 
 define BUSYBOX_UNINSTALL_TARGET_CMDS