linux-kernel - Re: [PATCH/RFC v5 01/57] leds: Add brightness_set

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Message-ID: <20150819193117.GA26567@amd>
Date:	Wed, 19 Aug 2015 21:31:17 +0200
From:	Pavel Machek <pavel@....cz>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
	cooloney@...il.com, rpurdie@...ys.net, stsp@...rs.sourceforge.net,
	Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH/RFC v5 01/57] leds: Add brightness_set_nonblocking op


> > >There are around 60 drivers in the other kernel subsystems that register
> > >LED class devices. If we chose the way you proposed then we would have
> > >to adjust all of them to the LED core changes, which could complicate
> > >the situation during merge window if there were other modifications in
> > >the affected drivers.
> 
> You don't need to change anything, if the semantics of
> brightness_set() does not change. All current drivers don't
> sleep. They use a work queue if needed to ensure they don't
> sleep. Hence they are correct.

Exactly. As you explain above, there are 60 reasons not to change
existing semantics.

> By adding a new operation, brightness_set_blocking(), you can strip
> out this work queue and move to the new op member one driver at a
> time. And you can take as long as you want doing this. No flag day
> when an API suddenly means something totally different.

Yes please.

									Pavel
-- 
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