linux-kernel - Re: [PATCHv4 4/7] hwspinlock/core: add common OF helpers

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Date:	Fri, 14 Mar 2014 10:23:04 -0500
From:	Josh Cartwright <joshc@...eaurora.org>
To:	Ohad Ben-Cohen <ohad@...ery.com>
Cc:	Bjorn Andersson <bjorn@...o.se>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Suman Anna <s-anna@...com>, Tony Lindgren <tony@...mide.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv4 4/7] hwspinlock/core: add common OF helpers

On Fri, Mar 14, 2014 at 03:12:26PM +0200, Ohad Ben-Cohen wrote:
> On Sun, Mar 2, 2014 at 10:19 PM, Bjorn Andersson <bjorn@...o.se> wrote:
> > When introducing the ability to reference a hwspin lock via a phandle
> > in device tree it makes a big difference to be able to differ between
> > the case of "initialization failed" or "device not yet probed"; so
> > that the client knows if it should fail or retry later.
> 
> I'm not convinced.
> 
> The only advantage this brings is to avoid retrying in case a fatal
> error has occurred. Such fatal errors are extremely rare, and when
> they show up - extremely painful, and I suspect that optimizing them
> wouldn't be a big win.

So, are you suggesting that because fatal errors should be "extremely
rare", a consuming driver should just assume that if NULL is returned
from a hwspin_lock_request*() function that it was the "device not yet
probed" case that was hit?

Note that having the consumer/hwspinlock device relationship modeled in
devicetree introduces more potential failure cases...

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