ledtrig-cpu: Limit to 8 CPUs

Some machines have thousands of CPUs... and trigger mechanisms was not
really meant for thousands of triggers. I doubt anyone uses this
trigger on many-CPU machine; but if they do, they'll need to do it
properly.
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/trigger/ledtrig-cpu.c

@@ -2,14 +2,18 @@
 /*
  * ledtrig-cpu.c - LED trigger based on CPU activity
  *
- * This LED trigger will be registered for each possible CPU and named as
- * cpu0, cpu1, cpu2, cpu3, etc.
+ * This LED trigger will be registered for first 8 CPUs and named
+ * as cpu0..cpu7. There's additional trigger called cpu that
+ * is on when any CPU is active.
+ *
+ * If you want support for arbitrary number of CPUs, make it one trigger,
+ * with additional sysfs file selecting which CPU to watch.
  *
  * It can be bound to any LED just like other triggers using either a
  * board file or via sysfs interface.
  *
  * An API named ledtrig_cpu is exported for any user, who want to add CPU
- * activity indication in their code
+ * activity indication in their code.
  *
  * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
  * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
@@ -145,6 +149,9 @@ static int __init ledtrig_cpu_init(void)
 	for_each_possible_cpu(cpu) {
 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 
+		if (cpu >= 8)
+			continue;
+
 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 
 		led_trigger_register_simple(trig->name, &trig->_trig);