1 // SPDX-License-Identifier: GPL-2.0-only
3  * ledtrig-cpu.c - LED trigger based on CPU activity
5  * This LED trigger will be registered for first 8 CPUs and named
6  * as cpu0..cpu7. There's additional trigger called cpu that
7  * is on when any CPU is active.
10  * with additional sysfs file selecting which CPU to watch.
15  * An API named ledtrig_cpu is exported for any user, who want to add CPU
19  * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
28 #include <linux/cpu.h>
31 #define MAX_NAME_LEN	8
45  * ledtrig_cpu - emit a CPU event as a trigger
46  * @evt: CPU event to be emitted
48  * Emit a CPU event on a CPU core, which will trigger a
54 	bool is_active = trig->is_active;  in ledtrig_cpu()
56 	/* Locate the correct CPU LED */  in ledtrig_cpu()
76 	if (is_active != trig->is_active) {  in ledtrig_cpu()
81 		trig->is_active = is_active;  in ledtrig_cpu()
82 		atomic_add(is_active ? 1 : -1, &num_active_cpus);  in ledtrig_cpu()
86 		led_trigger_event(trig->_trig,  in ledtrig_cpu()
119 static int ledtrig_online_cpu(unsigned int cpu)  in ledtrig_online_cpu()  argument
125 static int ledtrig_prepare_down_cpu(unsigned int cpu)  in ledtrig_prepare_down_cpu()  argument
133 	int cpu;  in ledtrig_cpu_init()  local
136 	/* Supports up to 9999 cpu cores */  in ledtrig_cpu_init()
142 	led_trigger_register_simple("cpu", &trig_cpu_all);  in ledtrig_cpu_init()
145 	 * Registering CPU led trigger for each CPU core here  in ledtrig_cpu_init()
146 	 * ignores CPU hotplug, but after this CPU hotplug works  in ledtrig_cpu_init()
149 	for_each_possible_cpu(cpu) {  in ledtrig_cpu_init()
150 		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);  in ledtrig_cpu_init()
152 		if (cpu >= 8)  in ledtrig_cpu_init()
155 		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);  in ledtrig_cpu_init()
157 		led_trigger_register_simple(trig->name, &trig->_trig);  in ledtrig_cpu_init()
165 		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",  in ledtrig_cpu_init()
168 	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");  in ledtrig_cpu_init()