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SubjectRe: [PATCH v5 3/3] leds: trigger: implement a tty trigger
Hi!

> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
> @@ -0,0 +1,6 @@
> +What: /sys/class/leds/<led>/dev
> +Date: Dec 2019
> +KernelVersion: 5.6
> +Contact: linux-leds@vger.kernel.org
> +Description:
> + Specifies $major:$minor of the triggering tty

Ok, sounds reasonable.

> +static ssize_t dev_store(struct device *dev,
> + struct device_attribute *attr, const char *buf,
> + size_t size)
> +{
> + struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
> + struct tty_struct *tty;
> + unsigned major, minor;
> + int ret;
> +
> + if (size == 0 || (size == 1 && buf[0] == '\n')) {
> + tty = NULL;
> + } else {
> + ret = sscanf(buf, "%u:%u", &major, &minor);
> + if (ret < 2)
> + return -EINVAL;

If user writes 1:2:badparsingofdata into the file, it will pass, right?

> + tty = tty_kopen_shared(MKDEV(major, minor));
> + if (IS_ERR(tty))
> + return PTR_ERR(tty);
> + }

Do you need to do some kind of tty_kclose()? What happens if the
device disappears, for example because the USB modem is unplugged?

> +static void ledtrig_tty_work(struct work_struct *work)
> +{
> + struct ledtrig_tty_data *trigger_data =
> + container_of(work, struct ledtrig_tty_data, dwork.work);
> + struct serial_icounter_struct icount;
> + int ret;
> +
> + if (!trigger_data->tty) {
> + led_set_brightness(trigger_data->led_cdev, LED_OFF);
> + return;
> + }
> +
> + ret = tty_get_icount(trigger_data->tty, &icount);
> + if (ret)
> + return;
> +
> + if (icount.rx != trigger_data->rx ||
> + icount.tx != trigger_data->tx) {
> + unsigned long delay_on = 100, delay_off = 100;
> +
> + led_blink_set_oneshot(trigger_data->led_cdev,
> + &delay_on, &delay_off, 0);
> +
> + trigger_data->rx = icount.rx;
> + trigger_data->tx = icount.tx;
> + }

Since you are polling this, anyway, can you just manipulate brightness
directly instead of using _oneshot()? _oneshot() will likely invoke
another set of workqueues.

LED triggers were meant to operate directly from the events, not based
on statistics like this.

Best regards,

Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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