linux-kernel - Re: [PATCH] ASoC: rt5651: use msleep for large delays

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Message-ID: <20170111180658.2yivagcwo4kgsp4e@sirena.org.uk>
Date:   Wed, 11 Jan 2017 18:06:58 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Nicholas Mc Guire <der.herr@...r.at>
Cc:     Nicholas Mc Guire <hofrat@...dl.org>,
        Bard Liao <bardliao@...ltek.com>,
        Oder Chiou <oder_chiou@...ltek.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: rt5651: use msleep for large delays

On Wed, Jan 11, 2017 at 03:06:45PM +0000, Nicholas Mc Guire wrote:
> On Wed, Jan 11, 2017 at 02:59:26PM +0000, Mark Brown wrote:

> > If you're doing conversions like this I'd expect us to be picking the
> > lower number rather than the higher number - people are saying "wait for
> > at least X and at most Y" and msleep() is "wait for at least X" so we
> > should be picking X.

> useleep_range() sets the timer to max and only if there happens to be a
> timer between min and max uses that - so the mean of runs is generally
> a bit above max. E.g.

Yes, but as fairly recently discussed somewhere on the lists (and IIRC
actually fixed) approximately no users expect or want that behaviour -
it's a really confusing interface given that sleep functions almost
always have a "delay up until X" interface and interfaces that can wake
things up earlier than the expected delay generally flag that condition.
The applications for the "delay for X but it's OK to wake me up this
much earlier" are really quite limited.  If you look at the conversions
that were done to usleep_range() you'll notice that most of them follow
this pattern and had their delays extended in the process.

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