linux-kernel - Re: [PATCH 1/2] mmc: dw_mmc: Handle late vmmc regulator with EPROBE

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Message-ID: <1841650.N6Drbs67FD@flatron>
Date:	Fri, 07 Jun 2013 12:30:52 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	Doug Anderson <dianders@...omium.org>, Chris Ball <cjb@...top.org>,
	Olof Johansson <olof@...om.net>,
	Andrew Bresticker <abrestic@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Will Newton <will.newton@...tec.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
	lgirdwood@...il.com
Subject: Re: [PATCH 1/2] mmc: dw_mmc: Handle late vmmc regulator with EPROBE_DEFER

On Friday 07 of June 2013 11:24:04 Mark Brown wrote:
> On Fri, Jun 07, 2013 at 12:19:58PM +0200, Tomasz Figa wrote:
> > On Thursday 06 of June 2013 21:46:45 Doug Anderson wrote:
> > > dw_mmc is probed.  This regulator is optional, though a warning will
> > > be printed if it's missing.  The fact that the regulator is optional
> > > means that (at the moment) it's not possible to use a regulator that
> > > probes _after_ dw_mmc.
> > > 
> > > Fix this limitation by adding the ability to make vmmc required.  If
> > > a
> > > vmmc-supply is specified in the device tree we'll assume that vmmc
> > > is
> > > required.
> > 
> > This interesting case makes me think that regulator core should
> > differentiate between regulator lookup failure due to no lookup
> > specified and due to the regulator specified in lookup being
> > unavailable, returning appropriate (different) error codes.
> 
> It does exactly that in so far as it can - you get -ENODEV if there's
> definitely no supply and -EPROBE_DEFER otherwise.

Oh, right, thanks. I somehow felt that it should be doing this already, 
but I was looking at 3.9 on Free Electron's LXR. It does so since commit

1e4b545cdd regulator: core: return err value for regulator_get if there is 
no DT binding

so I think this patch should be reworked to check the returned error code 
instead.

Best regards,
Tomasz

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