Hi Pavel,
On 9/19/20 11:38 AM, Pavel Machek wrote:
commit 318681d3e019e39354cc6c2155a7fd1bb8e8084d
Author: Pavel Machek <pavel@xxxxxx>
Date: Sat Sep 19 11:34:58 2020 +0200
ledtrig-cpu: Limit to 4 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@xxxxxx>
diff --git a/drivers/leds/trigger/ledtrig-cpu.c b/drivers/leds/trigger/ledtrig-cpu.c
index 869976d1b734..b7e00b09b137 100644
--- a/drivers/leds/trigger/ledtrig-cpu.c
+++ b/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 four CPUs and named
+ * as cpu0, cpu1, cpu2, cpu3. 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@xxxxxxxxxx>
* Copyright 2011 - 2012 Bryan Wu <bryan.wu@xxxxxxxxxxxxx>
@@ -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 > 4)
NACK. The workaround for this trigger was implemented for a reason -
to make it working on platforms with arbitrary number of logical cpus.
I've got 8, so I am discriminated now. Not saying, that it precludes
trigger registration with no single line of warning.
Regardless of that - you have no guarantee that you're not breaking
anyone - "I doubt" is not a sufficient argument.
+ continue;
+
snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
led_trigger_register_simple(trig->name, &trig->_trig);
--
Best regards,
Jacek Anaszewski
