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Date:	Thu, 20 Dec 2012 08:00:49 +1300
From:	Tony Prisk <>
To:	Russell King - ARM Linux <>
Cc:	Mike Turquette <>,,
	Arm Kernel Mailing List 
Subject: Re: Inconsistency in clk framework

On Thu, 2012-12-20 at 06:34 +1300, Tony Prisk wrote:
> On Wed, 2012-12-19 at 09:26 +0000, Russell King - ARM Linux wrote:
> > On Wed, Dec 19, 2012 at 05:10:33PM +1300, Tony Prisk wrote:
> > > Hi Mike,
> > > 
> > > In attempting to remove some IS_ERR_OR_NULL references, it was pointed
> > > out that clk_get() can return NULL if CONFIG_HAVE_CLK is not defined.
> > 
> > That is correct - but why is that a problem?  As far as users are
> > concerned, NULL is a valid clock.  If HAVE_CLK is undefined, do you
> > want all your drivers to suddenly stop working?
> That will be where the misunderstanding has occurred - I didn't consider
> NULL to be a valid clock.
> Given that NULL is a valid clock, I guess all tests against get_clk and
> of_get_clk results should be IS_ERR_OR_NULL. Correct?
For the sake of clarity, I should rephrase:

If the driver can't operate with a NULL clk, it should use a
IS_ERR_OR_NULL test to test for failure, rather than IS_ERR.

Tony P

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