Introduce ARCH_NO_SYSDEV_OPS config option (v2)

Introduce Kconfig option allowing architectures where sysdev
operations used during system suspend, resume and shutdown have been
completely replaced with struct sycore_ops operations to avoid
building sysdev code that will never be used.

Make callbacks in struct sys_device and struct sysdev_driver depend
on ARCH_NO_SYSDEV_OPS to allows us to verify if all of the references
have been actually removed from the code the given architecture
depends on.

Make x86 select ARCH_NO_SYSDEV_OPS.

Signed-off-by: Rafael J. Wysocki <[e-mail]>

arch/x86/Kconfig

···
 	select GENERIC_IRQ_SHOW
 	select IRQ_FORCED_THREADING
 	select USE_GENERIC_SMP_HELPERS if SMP
+	select ARCH_NO_SYSDEV_OPS
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)

drivers/base/Kconfig

···
 	bool
 	default n
 
+config ARCH_NO_SYSDEV_OPS
+	bool
+	---help---
+	  To be selected by architectures that don't use sysdev class or
+	  sysdev driver power management (suspend/resume) and shutdown
+	  operations.
+
 endmenu

drivers/base/sys.c

···
 }
 
 
-
+#ifndef CONFIG_ARCH_NO_SYSDEV_OPS
 /**
  *	sysdev_shutdown - Shut down all system devices.
  *
···
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sysdev_resume);
+#endif /* CONFIG_ARCH_NO_SYSDEV_OPS */
 
 int __init system_bus_init(void)
 {

include/linux/device.h

···
 /* drivers/base/power/shutdown.c */
 extern void device_shutdown(void);
 
+#ifndef CONFIG_ARCH_NO_SYSDEV_OPS
 /* drivers/base/sys.c */
 extern void sysdev_shutdown(void);
+#else
+static inline void sysdev_shutdown(void) { }
+#endif
 
 /* debugging and troubleshooting/diagnostic helpers. */
 extern const char *dev_driver_string(const struct device *dev);

include/linux/pm.h

···
  */
 
 #ifdef CONFIG_PM_SLEEP
-extern void device_pm_lock(void);
+#ifndef CONFIG_ARCH_NO_SYSDEV_OPS
+extern int sysdev_suspend(pm_message_t state);
 extern int sysdev_resume(void);
+#else
+static inline int sysdev_suspend(pm_message_t state) { return 0; }
+static inline int sysdev_resume(void) { return 0; }
+#endif
+
+extern void device_pm_lock(void);
 extern void dpm_resume_noirq(pm_message_t state);
 extern void dpm_resume_end(pm_message_t state);
 
 extern void device_pm_unlock(void);
-extern int sysdev_suspend(pm_message_t state);
 extern int dpm_suspend_noirq(pm_message_t state);
 extern int dpm_suspend_start(pm_message_t state);
 

include/linux/sysdev.h

···
 	const char *name;
 	struct list_head	drivers;
 	struct sysdev_class_attribute **attrs;
-
+	struct kset		kset;
+#ifndef CONFIG_ARCH_NO_SYSDEV_OPS
 	/* Default operations for these types of devices */
 	int	(*shutdown)(struct sys_device *);
 	int	(*suspend)(struct sys_device *, pm_message_t state);
 	int	(*resume)(struct sys_device *);
-	struct kset		kset;
+#endif
 };
 
 struct sysdev_class_attribute {
···
 	struct list_head	entry;
 	int	(*add)(struct sys_device *);
 	int	(*remove)(struct sys_device *);
+#ifndef CONFIG_ARCH_NO_SYSDEV_OPS
 	int	(*shutdown)(struct sys_device *);
 	int	(*suspend)(struct sys_device *, pm_message_t state);
 	int	(*resume)(struct sys_device *);
+#endif
 };