Kernel添加全局变量

参照下面的patch：

diff --git a/arch/arm/configs/xxx_defconfig b/arch/arm/configs/xxx_defconfig
index de0e7bf..93d7202 100644
--- a/arch/arm/configs/xxx_defconfig
+++ b/arch/arm/configs/xxx_defconfig
@@ -111,4 +111,5 @@ CONFIG_HAS_IOPORT_MAP=y
 CONFIG_HAS_DMA=m
 CONFIG_CPU_RMAP=y
 CONFIG_NLATTR=y
+CONFIG_ADD_GLOBAL_VAR=y
 # CONFIG_AVERAGE is not set
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index cc0ced0..60d968a 100755
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -84,3 +84,8 @@ config USB_OTG_FSM
	  Implements OTG Finite State Machine as specified in On-The-Go
	  and Embedded Host Supplement to the USB Revision 2.0 Specification.

+config ADD_GLOBAL_VAR
+	tristate "add global variable"
+	depends on USB
+	help
+	  add global variable.
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 8d5b2f4..a4ade71 100755
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -1039,6 +1039,10 @@ static void usb_debugfs_cleanup(void)
	debugfs_remove(usb_debug_root);
 }

+#ifdef CONFIG_ADD_GLOBAL_VAR
+extern unsigned int k_g_usb_state;
+#endif
+
 /*
  * Init
  */
@@ -1049,6 +1053,10 @@ static int __init usb_init(void)
		pr_info("%s: USB support disabled\n", usbcore_name);
		return 0;
	}
+
+    #ifdef CONFIG_ADD_GLOBAL_VAR
+    printk("[xxx] get global var,usb_state = %d\n", k_g_usb_state);
+    #endif
	usb_init_pool_max();

	retval = usb_debugfs_init();
@@ -1099,12 +1107,13 @@ out:
 /*
  * Cleanup
  */
+
 static void __exit usb_exit(void)
 {
	/* This will matter if shutdown/reboot does exitcalls. */
	if (usb_disabled())
		return;
-
+    
	usb_deregister_device_driver(&usb_generic_driver);
	usb_major_cleanup();
	usb_deregister(&usbfs_driver);
diff --git a/init/main.c b/init/main.c
index 1ed674b..196de9a 100755
--- a/init/main.c
+++ b/init/main.c
@@ -110,6 +110,11 @@ bool early_boot_irqs_disabled __read_mostly;
 enum system_states system_state __read_mostly;
 EXPORT_SYMBOL(system_state);

+#ifdef CONFIG_ADD_GLOBAL_VAR
+unsigned int k_g_usb_state = 2;
+EXPORT_SYMBOL(k_g_usb_state);
+#endif
+
 /*
  * Boot command-line arguments
  */