On Mon 2018-06-25 13:03:19, Baolin Wang wrote:
> From: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
>
> Some LED controllers have support for autonomously controlling
> brightness over time, according to some preprogrammed pattern or
> function.
>
> This adds a new optional operator that LED class drivers can implement
> if they support such functionality as well as a new device attribute to
> configure the pattern for a given LED.
Thanks for doing this!
> index 5f67f7a..fe90a12 100644
> --- a/Documentation/ABI/testing/sysfs-class-led
> +++ b/Documentation/ABI/testing/sysfs-class-led
> @@ -61,3 +61,19 @@ Description:
> gpio and backlight triggers. In case of the backlight trigger,
> it is useful when driving a LED which is intended to indicate
> a device in a standby like state.
> +
> +What: /sys/class/leds/<led>/pattern
> +Date: June 2018
> +KernelVersion: 4.18
> +Description:
> + Specify a pattern for the LED, for LED hardware that support
> + altering the brightness as a function of time.
> +
> + The pattern is given by a series of tuples, of brightness and
> + duration (ms). The LED is expected to traverse the series and
> + each brightness value for the specified duration.
> +
> + As LED hardware might have different capabilities and precision
> + the requested pattern might be slighly adjusted by the driver
> + and the resulting pattern of such operation should be returned
> + when this file is read.
I'd add "Duration of 0 means brightness should immediately change to
new value."
> + struct led_classdev *led_cdev = dev_get_drvdata(dev);
> + struct led_pattern *pattern = NULL;
> + unsigned long val;
> + char *sbegin;
> + char *elem;
> + char *s;
> + int ret, len = 0;
> + bool odd = true;
> +
> + s = sbegin = kstrndup(buf, size, GFP_KERNEL);
> + if (!s)
> + return -ENOMEM;
> +
> + /* Trim trailing newline */
> + s[strcspn(s, "\n")] = '\0';
Is substring function best to use here? Will it do the right thing
when \n is not present?
> + /* If the remaining string is empty, clear the pattern */
> + if (!s[0]) {
> + ret = led_cdev->pattern_clear(led_cdev);
> + goto out;
> + }
> +
> + pattern = kcalloc(size, sizeof(*pattern), GFP_KERNEL);
> + if (!pattern) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + /* Parse out the brightness & delta_t touples and check for repeat */
> + while ((elem = strsep(&s, " ")) != NULL) {
> + ret = kstrtoul(elem, 10, &val);
> + if (ret)
> + goto out;
> +
> + if (odd) {
> + pattern[len].brightness = val;
> + } else {
> + /* Ensure we don't have any delta_t == 0 */
> + if (!val) {
> + ret = -EINVAL;
> + goto out;
> + }
I believe we should support delta_t of 0 for "change immediately".
Thanks,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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