linux-kernel - Re: [PATCH 1/3] driver core: Add API to wait for deferred probe to complete during init

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Message-ID: <20130509135017.GD3200@sirena.org.uk>
Date:	Thu, 9 May 2013 14:50:17 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Ming Lei <tom.leiming@...il.com>,
	Saravana Kannan <skannan@...eaurora.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mike Turquette <mturquette@...aro.org>,
	Liam Girdwood <lrg@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH 1/3] driver core: Add API to wait for deferred probe to
 complete during init

On Thu, May 09, 2013 at 12:50:46PM +0100, Grant Likely wrote:

> However, if a device that shuts down resources after init has
> completed and then cannot turn those resources back on when another
> driver requests them then it sounds like there is a bigger design
> problem. We're in a hotplug world and most of the time a driver cannot
> assume that a resource will never get requested after initcalls have
> completed. It sounds like a design bug in the driver if it cannot
> handle that use case.

Even if the driver copes fine it can still be desirable to avoid the
power down/up cycle if it involves some user visible effect - things
like blinking the display off then on for example.  That said I am a
little suspicious about this approach, it doesn't feel as robust as it
should to go round individual callers.

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