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

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Message-ID: <20221030201527.GA23195@duo.ucw.cz>
Date:   Sun, 30 Oct 2022 21:15:27 +0100
From:   Pavel Machek <pavel@....cz>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>
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

Hi!

> >> 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.

Are there other solutions possible? Like batch and always apply _all_
the updates you have queued from your the worker code?

Best regards,
								Pavel

-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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