linux-kernel - Re: [RFC PATCH] led: add Cycle LED trigger.

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Message-ID: <1371593140.2038.8.camel@joe-AO722>
Date:	Tue, 18 Jun 2013 15:05:40 -0700
From:	Joe Perches <joe@...ches.com>
To:	Gaël PORTAY <g.portay@...rkiz.com>
Cc:	Rob Landley <rob@...dley.net>, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	"Milo(Woogyom) Kim" <milo.kim@...com>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [RFC PATCH] led: add Cycle LED trigger.

On Tue, 2013-06-18 at 18:24 +0200, Gaël PORTAY wrote:
> Currently, none of available triggers supports playing with the LED brightness
> level.  The cycle trigger provides a way to define custom brightness cycle.
> For example, it is easy to customize the cycle to mock up the rhythm of human
> breathing which is a nice cycle to tell the user the system is doing something.

I think maybe this is a userspace thing, but here's a
trivial comment or two


> +static int cycle_start(struct cycle_trig_data *data)
> +{
> +	unsigned long flags;
> +
> +	if (hrtimer_active(&data->timer))
> +		return -EINVAL;
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +	data->plot_index = 0;
> +	data->cycle_count = 0;
> +	hrtimer_start(&data->timer, ktime_get(), HRTIMER_MODE_ABS);
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	return 1;

Maybe return 0 on success

> +static ssize_t cycle_control_store(struct device *dev,
> +				    struct device_attribute *attr,
> +				    const char *buf, size_t size)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct cycle_trig_data *data = led_cdev->trigger_data;
> +
> +	if (strncmp(buf, "start", sizeof("start") - 1) == 0)
> +		cycle_start(data);
> +	else if (strncmp(buf, "stop", sizeof("stop") - 1) == 0)
> +		cycle_stop(data);
> +	else if (strncmp(buf, "reset", sizeof("reset") - 1) == 0)
> +		cycle_reset(data);
> +	else if (strncmp(buf, "pause", sizeof("stop") - 1) == 0)
> +		cycle_pause(data);
> +	else if (strncmp(buf, "resume", sizeof("resume") - 1) == 0)
> +		cycle_resume(data);
> +	else
> +		return -EINVAL;

I think strcasecmp better than strncmp

> +static ssize_t cycle_rawplot_store(struct device *dev,
> +                                  struct device_attribute *attr,
> +                                  const char *buf, size_t size)
> +{
[]
+       plot = kzalloc(size, GFP_KERNEL);
+       if (plot) {
+               hrtimer_cancel(&data->timer);

Ick.

	if (!plot)
		return -ENOMEM;

	etc...

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