linux-kernel - Re: [PATCH] clk: return proper ERR_PTR for clk_get when !HAVE

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Message-ID: <20150207164209.GA6263@katana>
Date:	Sat, 7 Feb 2015 17:42:09 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: return proper ERR_PTR for clk_get when !HAVE_CLK

On Thu, Feb 05, 2015 at 11:40:40PM +0000, Russell King - ARM Linux wrote:
> On Thu, Feb 05, 2015 at 08:09:22PM +0100, Wolfram Sang wrote:
> > clk_get functions return an ERR_PTR and not NULL in the error case. Make
> > that consistent for the dummy functions when HAVE_CLK is not enabled.
> > Otherwise unexpected codepaths might be trying to use a NULL pointer.
> 
> NAK.
> 
> There are some drivers which rely on this behaviour (take a driver,
> such as some PXA IP) which uses the clk API but is also reused on
> x86 which doesn't.

Okay, thanks for the explanation. Let me recap, there are three cases
that clk_get can return:

a) pointer to a clk
b) ERR_PTR meaning something went wrong when trying to get a clk
c) NULL meaning there is no clk to get

So, if this patch from i2c/for-next [1] wants to add optional clk
support, it should fallback to the old handling not by checking for
(!IS_ERR()) but for (!IS_ERR_OR_NULL()).

Correct?

[1] https://git.kernel.org/cgit/linux/kernel/git/wsa/linux.git/commit/?h=i2c/for-next&id=e961a094afe04c6c8ca1adac50c8d16513f31b93


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