Hi Baolin, On 08/06/2018 03:53 AM, Baolin Wang wrote: > Hi Jacek, [...] >>> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern >>> @@ -0,0 +1,21 @@ >>> +What: /sys/class/leds/<led>/pattern >>> +Date: August 2018 >>> +KernelVersion: 4.19 >>> +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. Duration of >>> + 0 means brightness should immediately change to new value. >>> + >>> + The format of the pattern values should be: >>> + "brightness_1 duration_1 brightness_2 duration_2 brightness_3 >>> + duration_3 ...". >>> + >>> +What: /sys/class/leds/<led>/repeat >>> +Date: August 2018 >>> +KernelVersion: 4.19 >>> +Description: >>> + Specify a pattern repeat number. 0 means repeat indefinitely. >> >> In current implementation this file on read returns the number >> of remaining repeat intervals. I'd add that to this description. > > I saw Pavel's comments that he did not suggest do this. So I will keep > the original description?
Yes, please report always the original value. [...] >>> +static ssize_t pattern_trig_store_repeat(struct device *dev, >>> + struct device_attribute *attr, >>> + const char *buf, size_t count) >>> +{ >>> + struct led_classdev *led_cdev = dev_get_drvdata(dev); >>> + struct pattern_trig_data *data = led_cdev->trigger_data; >>> + unsigned long res; >>> + int err; >>> + >>> + err = kstrtoul(buf, 10, &res); >>> + if (err) >>> + return err; >>> + >>> + if (!led_cdev->pattern_set) >>> + del_timer_sync(&data->timer); >> >> Is there a reason for not having this check under mutex? > > We will hold the mutex in pattern_trig_timer_function(), so if we do > del_timer_sync() under the mutex protection, we may meet dead-lock > issue. Moreover, the del_timer_sync() will make sure deactivating one > timer is safe. Ack. -- Best regards, Jacek Anaszewski