clockevents: Provide sysfs interface

Provide a simple sysfs interface for the clockevent devices. Show the
current active clockevent device.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143436.371634778@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 86 insertions, 0 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 89e394caa769..0a23f4f29934 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -16,6 +16,7 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/smp.h>
+#include <linux/device.h>
 
 #include "tick-internal.h"
 
@@ -460,4 +461,89 @@ void clockevents_notify(unsigned long reason, void *arg)
         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 }
 EXPORT_SYMBOL_GPL(clockevents_notify);
+
+#ifdef CONFIG_SYSFS
+struct bus_type clockevents_subsys = {
+        .name           = "clockevents",
+        .dev_name       = "clockevent",
+};
+
+static DEFINE_PER_CPU(struct device, tick_percpu_dev);
+static struct tick_device *tick_get_tick_dev(struct device *dev);
+
+static ssize_t sysfs_show_current_tick_dev(struct device *dev,
+                                           struct device_attribute *attr,
+                                           char *buf)
+{
+        struct tick_device *td;
+        ssize_t count = 0;
+
+        raw_spin_lock_irq(&clockevents_lock);
+        td = tick_get_tick_dev(dev);
+        if (td && td->evtdev)
+                count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
+        raw_spin_unlock_irq(&clockevents_lock);
+        return count;
+}
+static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+static struct device tick_bc_dev = {
+        .init_name      = "broadcast",
+        .id             = 0,
+        .bus            = &clockevents_subsys,
+};
+
+static struct tick_device *tick_get_tick_dev(struct device *dev)
+{
+        return dev == &tick_bc_dev ? tick_get_broadcast_device() :
+                &per_cpu(tick_cpu_device, dev->id);
+}
+
+static __init int tick_broadcast_init_sysfs(void)
+{
+        int err = device_register(&tick_bc_dev);
+
+        if (!err)
+                err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
+        return err;
+}
+#else
+static struct tick_device *tick_get_tick_dev(struct device *dev)
+{
+        return &per_cpu(tick_cpu_device, dev->id);
+}
+static inline int tick_broadcast_init_sysfs(void) { return 0; }
 #endif
+
+static int __init tick_init_sysfs(void)
+{
+        int cpu;
+
+        for_each_possible_cpu(cpu) {
+                struct device *dev = &per_cpu(tick_percpu_dev, cpu);
+                int err;
+
+                dev->id = cpu;
+                dev->bus = &clockevents_subsys;
+                err = device_register(dev);
+                if (!err)
+                        err = device_create_file(dev, &dev_attr_current_device);
+                if (err)
+                        return err;
+        }
+        return tick_broadcast_init_sysfs();
+}
+
+static int __init clockevents_init_sysfs(void)
+{
+        int err = subsys_system_register(&clockevents_subsys, NULL);
+
+        if (!err)
+                err = tick_init_sysfs();
+        return err;
+}
+device_initcall(clockevents_init_sysfs);
+#endif /* SYSFS */
+
+#endif /* GENERIC_CLOCK_EVENTS */