linux-kernel - Re: [RFC PATCH v1 1/1] leds: support to use own workqueue for each LED

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Date:   Sun, 30 Oct 2022 14:01:23 +0000
From:   Arseniy Krasnov <AVKrasnov@...rdevices.ru>
To:     Pavel Machek <pavel@....cz>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>
Subject: Re: [RFC PATCH v1 1/1] leds: support to use own workqueue for each
 LED

On 30.10.2022 15:20, Pavel Machek wrote:
> On Sun 2022-10-30 06:07:05, Arseniy Krasnov wrote:
>> This allows to set own workqueue for each LED. This may be useful, because
>> default 'system_wq' does not guarantee execution order of each work_struct,
>> thus for several brightness update requests (for multiple leds), real
>> brightness switch could be in random order.
> 
> So.. what?
> 
> Even if execution order is switched, human eye will not be able to
> tell the difference.
Hello,

Problem arises on one of our boards where we have 14 triples of leds(each
triple contains R G B). Test case is to play complex animation on all leds:
smooth switch from on RGB state to another. Sometimes there are glitches in
this process - divergence from expectable RGB state. We fixed this by using
ordered workqueue.

Thanks, Arseniy

> 								Pavel