[PATCH] Driver Core: Add /sys/hypervisor when needed

To have a home for all hypervisors, this patch creates /sys/hypervisor.
A new config option SYS_HYPERVISOR is introduced, which should to be set
by architecture dependent hypervisors (e.g. s390 or Xen).

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/Kconfig

@@ -38,3 +38,7 @@ config DEBUG_DRIVER
 	  If you are unsure about this, say N here.
 
 endmenu
+
+config SYS_HYPERVISOR
+	bool
+	default n

drivers/base/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_FW_LOADER)	+= firmware_class.o
 obj-$(CONFIG_NUMA)	+= node.o
 obj-$(CONFIG_MEMORY_HOTPLUG) += memory.o
 obj-$(CONFIG_SMP)	+= topology.o
+obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
 
 ifeq ($(CONFIG_DEBUG_DRIVER),y)
 EXTRA_CFLAGS += -DDEBUG

drivers/base/base.h

@@ -5,6 +5,11 @@ extern int devices_init(void);
 extern int buses_init(void);
 extern int classes_init(void);
 extern int firmware_init(void);
+#ifdef CONFIG_SYS_HYPERVISOR
+extern int hypervisor_init(void);
+#else
+static inline int hypervisor_init(void) { return 0; }
+#endif
 extern int platform_bus_init(void);
 extern int system_bus_init(void);
 extern int cpu_dev_init(void);

drivers/base/hypervisor.c

@@ -0,0 +1,19 @@
+/*
+ * hypervisor.c - /sys/hypervisor subsystem.
+ *
+ * This file is released under the GPLv2
+ *
+ */
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+
+#include "base.h"
+
+decl_subsys(hypervisor, NULL, NULL);
+EXPORT_SYMBOL_GPL(hypervisor_subsys);
+
+int __init hypervisor_init(void)
+{
+	return subsystem_register(&hypervisor_subsys);
+}

drivers/base/init.c

@@ -27,6 +27,7 @@ void __init driver_init(void)
 	buses_init();
 	classes_init();
 	firmware_init();
+	hypervisor_init();
 
 	/* These are also core pieces, but must come after the
 	 * core core pieces.

include/linux/kobject.h

@@ -190,6 +190,8 @@ struct subsystem _varname##_subsys = { \
 
 /* The global /sys/kernel/ subsystem for people to chain off of */
 extern struct subsystem kernel_subsys;
+/* The global /sys/hypervisor/ subsystem  */
+extern struct subsystem hypervisor_subsys;
 
 /**
  * Helpers for setting the kset of registered objects.