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    SubjectRe: [PATCH 01/18] led-triggers: create a trigger for CPU activity
    On Wed, Apr 18, 2012 at 6:52 AM, Andrew Morton
    <akpm@linux-foundation.org> wrote:
    > On Tue, 17 Apr 2012 18:53:28 +0800
    > Bryan Wu <bryan.wu@canonical.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@canonical.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@rpsys.net>
    >> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    >> Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
    >>
    >
    > A spurious newline.
    >

    OK, Fixed

    >> Reviewed-by: Jamie Iles <jamie@jamieiles.com>
    >> Tested-by: Jochen Friedrich <jochen@scram.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@linaro.org>");
    >> +MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.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@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel



    --
    Bryan Wu <bryan.wu@canonical.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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