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    SubjectRe: [PATCH ] leds: add new transient trigger for one shot timer support
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    >
    > Are there no comments from anyone on this?
    Thanks for the comments.
    >
    > >
    > > ...
    > >
    > > config LEDS_TRIGGER_TRANSIENT
    > > + tristate "LED Transient Trigger"
    > > + depends on LEDS_TRIGGERS
    > > + help
    > > + This allows one time enable of a transient state on GPIO/PWM based
    > > + hadrware.
    >
    > Make it "This allows one time enabling of a transient state on GPIO/PWM
    > based hardware."
    Will do.
    >
    > > + If unsure, say Y.
    > > +
    > >
    > > ...
    > >
    > > +static void transient_timer_function(unsigned long data)
    > > +{
    > > + struct led_classdev *led_cdev = (struct led_classdev *) data;
    > > + struct transient_trig_data *transient_data = led_cdev->trigger_data;
    > > +
    > > + if (transient_data->transient_enabled) {
    > > + transient_data->transient_enabled = 0;
    > > + led_cdev->brightness_set(led_cdev, LED_OFF);
    > > + del_timer(&transient_data->timer);
    >
    > Deleting the timer from within its handler is ... odd. Also it is a
    > bit racy against a concurrent add_timer() on a different CPU.
    Good point. Will fix.
    >
    > > + }
    > > +}
    > > +
    > >
    > > ...
    > >
    > > +static ssize_t led_transient_enabled_store(struct device *dev,
    > > + struct device_attribute *attr, const char *buf, size_t size)
    > > +{
    > > + struct led_classdev *led_cdev = dev_get_drvdata(dev);
    > > + struct transient_trig_data *transient_data = led_cdev->trigger_data;
    > > + unsigned long state;
    > > + ssize_t ret = -EINVAL;
    > > +
    > > + ret = kstrtoul(buf, 10, &state);
    > > + if (ret)
    > > + return ret;
    > > +
    > > + if (state != 1 && state != 0)
    > > + return ret;
    >
    > Bug - we'll return 0 here. Use "return -EINVAL" and remove the above
    > initialisation of `ret'.

    Good point. Will fix.
    >
    >
    > > + /* cancel the running timer */
    > > + if (state == 0) {
    > > + transient_timer_function((unsigned long) led_cdev);
    >
    > And this is perhaps why transient_timer_function() does del_timer().
    >
    > I suggest it would be cleaner and simpler to do
    >
    > transient_data->transient_enabled = 0;
    > del_timer(...);
    >
    > right here.

    Will fix it.
    >
    > This is all rather racy in its handling of ->transient_enabled (at
    > least), but afacit the races are harmless.

    I am a bit concerned about it as well. Does adding a mutex to
    trigger_data a good way to go to protect transient_enabled? I will give
    that a try.

    > The typecast is unneeded.
    ok
    >
    > > + /* start timer with transient_time value */
    > > + if (state == 1 && transient_data->transient_time != 0) {
    > > + led_cdev->brightness_set(led_cdev, LED_FULL);
    > > + mod_timer(&transient_data->timer,
    > > + jiffies + transient_data->transient_time);
    > > + }
    > > +
    > > + return size;
    > > +}
    > > +
    > >
    > > ...
    > >
    > > +static ssize_t led_transient_time_store(struct device *dev,
    > > + struct device_attribute *attr, const char *buf, size_t size)
    > > +{
    > > + struct led_classdev *led_cdev = dev_get_drvdata(dev);
    > > + struct transient_trig_data *transient_data = led_cdev->trigger_data;
    > > + unsigned long state;
    > > + ssize_t ret = -EINVAL;
    >
    > Unneeded initialisation.
    Yup
    >
    > > + ret = kstrtoul(buf, 10, &state);
    > > + if (ret)
    > > + return ret;
    > > +
    > > + transient_data->transient_time = state;
    > > +
    > > + return size;
    > > +}
    > > +
    > >
    > > ...
    > >
    > > +static void transient_trig_deactivate(struct led_classdev *led_cdev)
    > > +{
    > > + struct transient_trig_data *transient_data = led_cdev->trigger_data;
    > > +
    > > + if (led_cdev->activated) {
    > > + device_remove_file(led_cdev->dev, &dev_attr_transient_enabled);
    > > + device_remove_file(led_cdev->dev, &dev_attr_transient_time);
    > > + del_timer_sync(&transient_data->timer);
    > > + led_cdev->trigger_data = NULL;
    > > + led_cdev->activated = false;
    > > + kfree(transient_data);
    >
    > OK. But it might be nicer to kill off the timer before doing anything else.
    Yes that is correct - will fix it.
    >
    > > + }
    > > + printk(KERN_DEBUG "Deativated led transient trigger %s\n",
    > > + led_cdev->name);
    > > +}
    > > +
    > >
    > > ...
    > >
    >
    > --
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