linux-kernel - Re: [PATCH 1/7] mmc: dw_mmc: lookup for optional biu and ciu clocks

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Date:	Thu, 10 May 2012 14:43:42 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	James Hogan <james@...anarts.com>
Cc:	Thomas Abraham <thomas.abraham@...aro.org>,
	linux-samsung-soc@...r.kernel.org, patches@...aro.org,
	devicetree-discuss@...ts.ozlabs.org, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, rob.herring@...xeda.com,
	grant.likely@...retlab.ca, kgene.kim@...sung.com, cjb@...top.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/7] mmc: dw_mmc: lookup for optional biu and ciu clocks

On Wed, May 02, 2012 at 03:53:53PM +0100, James Hogan wrote:
> Hi
> 
> On 2 May 2012 06:07, Thomas Abraham <thomas.abraham@...aro.org> wrote:
> > +       if (IS_ERR(host->biu_clk))
> > +               dev_info(&host->dev, "biu clock not available\n");
> 
> In this case, should it set host->biu_clk to NULL or are clk_disable
> and clk_put guaranteed to handle an IS_ERR value?

I keep saying this.  NULL must be treated as a valid reutrn value from
clk_get() and must not use this as a sentinel.  The clk namespace is
that errors are indicated with IS_ERR(clk) returning true.  Everything
else must be assumed to be valid by drivers.
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