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From: Pavel Machek <pavel@ucw.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: David Lin <dtwlin@google.com>,
	rpurdie@rpsys.net, robh@kernel.org, romlem@google.com,
	joelaf@google.com, stable@vger.kernel.org,
	linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] led: ledtrig-transient: replace timer_list with hrtimer
Date: Mon, 24 Apr 2017 22:18:29 +0200	[thread overview]
Message-ID: <20170424201829.GA18679@amd> (raw)
In-Reply-To: <d6b3d00b-938a-e61e-ce6d-96adacf73396@gmail.com>

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Hi!
> Hi David,
> 
> Thanks for the patch.
> 
> Unfortunately we cannot switch to using hr timers just like that
> without introducing side effects for many devices. We had similar
> attempt of increasing timer tirgger accuracy two years ago [0].
> 
> In short words, for drivers that can sleep while setting brightness
> and/or are using a bus like I2C you will not be able to enforce
> 1ms delay period.
> 
> I recommend you to go through the thread [0] so that we had
> a well defined ground for the discussion on how to address this
> issue properly.
> 
> Alternatively, in order to avoid all quirks related to LED subsystem,
> I'd propose to implement this feature in the GPIO subsystem, which
> seems to be more suitable place for it.

Actually.. make that "implement it in force feedback subsystem where
it belongs". And we actually have force feedback subsystem, already,
see drivers/input/ff-core.c .

(Nokia N900 actually uses that subsystem for the vibration motor, so
there's existing code...)

Thanks,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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  reply	other threads:[~2017-04-24 20:18 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-24  4:42 [PATCH] led: ledtrig-transient: replace timer_list with hrtimer David Lin
2017-04-24  7:44 ` Pavel Machek
2017-04-24 19:59 ` Jacek Anaszewski
2017-04-24 20:18   ` Pavel Machek [this message]
2017-04-25  3:05   ` David Lin
2017-04-25 20:15     ` Jacek Anaszewski
2017-04-27  3:48       ` David Lin
2017-04-27 18:37         ` Jacek Anaszewski
2017-04-25 22:34     ` Pavel Machek
2017-04-26 19:49       ` Jacek Anaszewski

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