From: Pavel Machek <pavel@ucw.cz>
To: "Bollinger, Seth" <Seth.Bollinger@digi.com>
Cc: "linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
Dan Murphy <dmurphy@ti.com>, Seth Bollinger <seth.boll@gmail.com>
Subject: Re: Strange timer LED behavior
Date: Mon, 19 Oct 2020 16:06:17 +0200 [thread overview]
Message-ID: <20201019140617.GA25480@duo.ucw.cz> (raw)
In-Reply-To: <A2C38AF0-0CE8-4312-8329-54B7E9653223@digi.com>
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Hi!
> We use the sysfs timer trigger of the led subsystem to control our leds (turn on, turn off, and blink). While doing this we found a strange behavior. If the values of delay_on and delay_off are ever both zero, the led subsystem will make the decision to blink at a 500ms on and 500ms off rate.
>
> # cd /sys/class/leds/g01
> # cat delay_on
> 0
> # cat delay_off
> 86400
> # echo 0 > delay_off
> # cat delay_on
> 500
> # cat delay_off
> 500
>
> drivers/led/led-core.c:184
> /* blink with 1 Hz as default if nothing specified */
> if (!*delay_on && !*delay_off)
> *delay_on = *delay_off = 500;
>
> Is there a reason that the kernel would decide to blink at this default rate instead of leaving the timer disabled?
>
Yep. It allows hardware to provide different values if it can only
blink at fixed rate.
Pavel
--
http://www.livejournal.com/~pavelmachek
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next prev parent reply other threads:[~2020-10-19 14:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 13:08 Strange timer LED behavior Bollinger, Seth
2020-10-19 14:06 ` Pavel Machek [this message]
2020-10-19 14:16 ` Bollinger, Seth
2020-10-20 12:04 ` Bollinger, Seth
2020-10-20 12:21 ` Pavel Machek
2020-10-20 12:31 ` Bollinger, Seth
2020-10-20 18:08 ` Pavel Machek
2020-10-20 18:28 ` Bollinger, Seth
2020-10-20 18:33 ` Pavel Machek
2020-10-20 18:35 ` Bollinger, Seth
2020-10-20 18:40 ` Pavel Machek
2020-10-20 18:51 ` Bollinger, Seth
2020-10-22 10:06 ` Pavel Machek
2020-10-22 11:34 ` Bollinger, Seth
2020-10-24 7:45 ` Pavel Machek
2020-10-21 20:23 ` Jacek Anaszewski
2020-10-22 11:35 ` Bollinger, Seth
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