linux-kernel - Re: [PATCH/RFC RESEND] leds: Use set_brightness_work for brightness

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Date:	Tue, 30 Jun 2015 14:41:08 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>,
	Stas Sergeev <stsp@...rs.sourceforge.net>
CC:	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Pavel Machek <pavel@....cz>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Andreas Werner <andreas.werner@....de>,
	Andrew Lunn <andrew@...n.ch>,
	Antonio Ospite <ospite@...denti.unina.it>,
	Atsushi Nemoto <anemo@....ocn.ne.jp>,
	Ben Dooks <ben@...tec.co.uk>, Chris Boot <bootc@...tc.net>,
	Dan Murphy <dmurphy@...com>,
	Daniel Jeong <daniel.jeong@...com>,
	Daniel Mack <daniel@...que.org>,
	"David S. Miller" <davem@...emloft.net>,
	Fabio Baltieri <fabio.baltieri@...il.com>,
	Felipe Balbi <balbi@...com>,
	Florian Fainelli <florian@...nwrt.org>,
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	Kristian Kielhofner <kris@...sk.org>,
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	"Sebastian A. Siewior" <bigeasy@...utronix.de>,
	Shuah Khan <shuahkhan@...il.com>,
	Simon Guinot <sguinot@...ie.com>,
	Álvaro Fernández Rojas <noltari@...il.com>
Subject: Re: [PATCH/RFC RESEND] leds: Use set_brightness_work for brightness_set
 ops that can sleep

30.06.2015 11:27, Jacek Anaszewski пишет:
> On 06/29/2015 05:17 PM, Stas Sergeev wrote:> 29.06.2015 17:05, Jacek Anaszewski пишет:
>>> +         * If need to disable soft blinking delegate this to the
>>> +         * work queue task to avoid problems in case we are
>>> +         * called from hard irq context.
>>> +         */
>>> +        led_cdev->flags |= LED_BLINK_DISABLE;
>> Wouldn't it be better to just enforce the callers
>> to explicitly disable software blink, so that it to
>> never happen from irq context? Something like in this
>> patch:
>> https://lkml.org/lkml/2015/5/13/491
>>
> 
> Blinking can be disabled not only by removing trigger explicitly,
> but also by setting brightness to 0 and led_set_brightness
> can be called from hard irq context. set_brightness_work
> was originally introduced exactly for this use case.
Could you please describe where does this happen?
I can see LED_OFF happening only in led_heartbeat_function(), but
it doesn't use soft-blink, so it will not activate the delayed
timer cancel.

I would suggest the patch below to make it explicit that
led_heartbeat_function() doesn't want to cancel soft blink.
Note that led_heartbeat_function() already uses led_set_brightness_async()
in a normal case.


diff --git a/drivers/leds/trigger/ledtrig-heartbeat.c b/drivers/leds/trigger/ledtrig-heartbeat.c
index fea6871..0f89d12 100644
--- a/drivers/leds/trigger/ledtrig-heartbeat.c
+++ b/drivers/leds/trigger/ledtrig-heartbeat.c
@@ -37,7 +37,7 @@ static void led_heartbeat_function(unsigned long data)
 	unsigned long delay = 0;

 	if (unlikely(panic_heartbeats)) {
-		led_set_brightness(led_cdev, LED_OFF);
+		led_set_brightness_async(led_cdev, LED_OFF);
 		return;
 	}

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