linux-kernel - Re: [PATCH v2] clk: Propagate prepare and enable when reparenting orphans

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Message-ID: <20141120100633.GP4042@n2100.arm.linux.org.uk>
Date:	Thu, 20 Nov 2014 10:06:33 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Mike Turquette <mturquette@...aro.org>,
	Heiko Stuebner <heiko@...ech.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] clk: Propagate prepare and enable when reparenting
 orphans

On Wed, Nov 19, 2014 at 11:45:14PM -0800, Dmitry Torokhov wrote:
> On Wed, Nov 19, 2014 at 09:15:41PM -0800, Doug Anderson wrote:
> > I will defer to your wisdom here.  I agree that these are the two
> > primary solutions and I've picked one, but I have no idea which will
> > be more of a PITA in the long run.
> > 
> > Note: I'm not sure that anyone expects EPROBE_DEFER to be returned
> > from a clk_enable() (do they?).  It almost seems like the right answer
> > is to fail to allow anyone to clk_get() any clock that doesn't have a
> > path to root.
> 
> EPROBE_DEFER only makes sense in driver's probe paths and so I would be
> very against adding it to clk_enable() which is called from many places
> in the kernel. If we decide to go with EPROBE_DEFER then returning it
> from clk_get() seems like a much better choice since it is normally
> called during probing.

Absolutely correct.  EINVAL would be better for clk_prepare() since it
isn't something that can be recovered from by just retrying a bit later.

You're absolutely correct that EPROBE_DEFER has no business being returned
in any path other than a driver's probe function; it is not a user visible
error code, it is a special internal Linux error code which only the driver
model understands to mean "add this device to the deferred probe list and
try again a while later."  Userspace, especially, should never see this
error code.

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