cpu: Register a generic CPU device on architectures that currently do not

frv, h8300, m68k, microblaze, openrisc, score, um and xtensa currently
do not register a CPU device.  Add the config option GENERIC_CPU_DEVICES
which causes a generic CPU device to be registered for each present CPU,
and make all these architectures select it.

Richard Weinberger <richard@nod.at> covered UML and suggested using
per_cpu.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 23 insertions, 0 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index e95c67edb2c..fcbec8ac134 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -172,6 +172,10 @@ config SYS_HYPERVISOR
         bool
         default n
 
+config GENERIC_CPU_DEVICES
+        bool
+        default n
+
 source "drivers/base/regmap/Kconfig"
 
 config DMA_SHARED_BUFFER
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index bba70d08be6..db87e78d745 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -11,6 +11,7 @@
 #include <linux/device.h>
 #include <linux/node.h>
 #include <linux/gfp.h>
+#include <linux/percpu.h>
 
 #include "base.h"
 
@@ -275,11 +276,29 @@ bool cpu_is_hotpluggable(unsigned cpu)
 }
 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 
+#ifdef CONFIG_GENERIC_CPU_DEVICES
+static DEFINE_PER_CPU(struct cpu, cpu_devices);
+#endif
+
+static void __init cpu_dev_register_generic(void)
+{
+#ifdef CONFIG_GENERIC_CPU_DEVICES
+        int i;
+
+        for_each_possible_cpu(i) {
+                if (register_cpu(&per_cpu(cpu_devices, i), i))
+                        panic("Failed to register CPU device");
+        }
+#endif
+}
+
 void __init cpu_dev_init(void)
 {
         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
                 panic("Failed to register CPU subsystem");
 
+        cpu_dev_register_generic();
+
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
 #endif