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Date: Thu, 19 Apr 2012 10:44:57 +0800
From: Bryan Wu <bryan.wu@...onical.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: nicolas.pitre@...aro.org, linux@....linux.org.uk,
linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
rpurdie@...ys.net, arnd.bergmann@...aro.org,
tim.gardner@...onical.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 01/18] led-triggers: create a trigger for CPU activity
On Wed, Apr 18, 2012 at 6:52 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Tue, 17 Apr 2012 18:53:28 +0800
> Bryan Wu <bryan.wu@...onical.com> wrote:
>
>> Attempting to consolidate the ARM LED code, this removes the
>> custom RealView LED trigger code to turn LEDs on and off in
>> response to CPU activity and replace it with a standard trigger.
>>
>> (bryan.wu@...onical.com:
>> It moves arch/arm/kernel/leds.c syscore stubs into this trigger.
>
> No, the patch doesn't alter arch/arm/kernel/leds.c at all. This text
> is either misleadingly phrased, or stale or something.
>
OK, Fixed
>> It also provides ledtrig_cpu trigger event stub in <linux/leds.h>.
>> Although it was inspired by ARM work, it can be used in other arch.)
>>
>> Cc: Richard Purdie <rpurdie@...ys.net>
>> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>> Signed-off-by: Bryan Wu <bryan.wu@...onical.com>
>>
>
> A spurious newline.
>
OK, Fixed
>> Reviewed-by: Jamie Iles <jamie@...ieiles.com>
>> Tested-by: Jochen Friedrich <jochen@...am.de>
>>
>> ...
>>
>> +config LEDS_TRIGGER_CPU
>> + tristate "LED CPU Trigger"
>> + depends on LEDS_TRIGGERS
>> + help
>> + This allows LEDs to be controlled by active CPUs. This shows
>> + the active CPUs across an array of LEDs so you can see what
>
> s/what/which/ (I think ;))
>
Fixed
>> + CPUs are active on the system at any given moment.
>> +
>> + If unsure, say N.
>> +
>>
>> ...
>>
>> +static int __init ledtrig_cpu_init(void)
>> +{
>> + int cpu;
>> +
>> + /* Supports up to 9999 cpu cores */
>> + BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
>
> hm, I wonder if this can be prevented in Kconfig logic. I guess
> "depends on NR_CPUS <= 9999" isn't available.
>
"default N if (NR_CPUS > 9999)" isn't available, either.
>> + /*
>> + * Registering CPU led trigger for each CPU cores here
>
> s/cores/core/
>
Fixed
>> + * ignores CPU hotplug, but after this CPU hotplug works
>> + * fine with this trigger.
>> + */
>> + for_each_possible_cpu(cpu) {
>> + struct led_trigger *trig;
>> + char *name = per_cpu(trig_name, cpu);
>> + struct rw_semaphore *lock = &per_cpu(trig_lock, cpu);
>> +
>> + init_rwsem(lock);
>> +
>> + snprintf(name, MAX_NAME_LEN, "cpu%d", cpu);
>> +
>> + down_write(lock);
>> + led_trigger_register_simple(name, &trig);
>
> OK, problem.
>
> led_trigger_register_simple() calls kzalloc() and
> led_trigger_register(), both of which can fail.
> led_trigger_register_simple() just returns void, failing to propagate
> the error back. This is bad, and we (ie you ;)) should fix
> led_trigger_register_simple() before proceeding to use it. If at all
> possible. Please. Let us not propagate the badness further. Sorry.
>
>> + per_cpu(cpu_trig, cpu) = trig;
>> + up_write(lock);
>> + }
>> +
>> + register_syscore_ops(&ledtrig_cpu_syscore_ops);
>> +
>> + pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
>> +
>> + return 0;
>> +}
>> +module_init(ledtrig_cpu_init);
>> +
>> +static void __exit ledtrig_cpu_exit(void)
>> +{
>> + int cpu;
>> +
>> + for_each_possible_cpu(cpu) {
>> + struct led_trigger *trig = per_cpu(cpu_trig, cpu);
>
> grr. drivers/leds/led-triggers.c sometimes does
>
> struct led_trigger trigger;
>
> and sometimes
>
> struct led_trigger trig;
>
> which makes the code needlessly more difficult to follow. So if you're
> fiddling with drivers/leds/led-triggers.c, please fix that up - use
> "trig" everywhere?
>
If Richard has no objection, I will do this.
>> + char *name = per_cpu(trig_name, cpu);
>> +
>> + led_trigger_unregister_simple(trig);
>
> And what happens if led_trigger_register_simple() had silently failed
> to register this trigger? afacit, nothing: your code handles the
> trig==NULL case OK. Still, we should be checking for those failures!
>
>> + per_cpu(cpu_trig, cpu) = NULL;
>> + memset(name, 0, MAX_NAME_LEN);
>> + }
>> +
>> + unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
>> +}
>> +module_exit(ledtrig_cpu_exit);
>> +
>> +MODULE_AUTHOR("Linus Walleij <linus.walleij@...aro.org>");
>> +MODULE_AUTHOR("Bryan Wu <bryan.wu@...onical.com>");
>> +MODULE_DESCRIPTION("CPU LED trigger");
>> +MODULE_LICENSE("GPL");
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index 5884def..1215b94 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -210,4 +210,27 @@ struct gpio_led_platform_data {
>> struct platform_device *gpio_led_register_device(
>> int id, const struct gpio_led_platform_data *pdata);
>>
>> +enum cpu_led_event {
>> + CPU_LED_IDLE_START, /* CPU enters idle */
>> + CPU_LED_IDLE_END, /* CPU idle ends */
>> + CPU_LED_START, /* Machine starts, especially resume */
>> + CPU_LED_STOP, /* Machine stops, especially suspend */
>> + CPU_LED_HALTED, /* Machine shutdown */
>> +};
>> +#if defined(CONFIG_LEDS_TRIGGER_CPU) || defined(CONFIG_LEDS_TRIGGER_CPU_MODULE)
>
> See lkml subject "RFC: strip 15,000 lines from a typical autoconf.h".
> We might be able to simplify this. But the above is OK for now.
>
>> +/**
>> + * ledtrig_cpu - emit a CPU event as a trigger
>> + * @evt: CPU event to be emitted
>> + *
>> + * Emit a CPU event on a CPU core, which will trigger a
>> + * binded LED to turn on or turn off.
>> + */
>
> It's conventional to add kerneldoc at the function definition site, not
> at the declaration. Nobody thinks to look in the .h file for
> documentation.
>
Fixed.
>> +extern void ledtrig_cpu(enum cpu_led_event evt);
>> +#else
>> +static inline void ledtrig_cpu(enum cpu_led_event evt)
>> +{
>> + return;
>> +}
>> +#endif
>> +
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
--
Bryan Wu <bryan.wu@...onical.com>
Kernel Developer +86.186-168-78255 Mobile
Canonical Ltd. www.canonical.com
Ubuntu - Linux for human beings | www.ubuntu.com
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