Date: Sat, 7 Feb 2015 17:42:09 +0100
From: Wolfram Sang <wsa@the-dreams.de>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] clk: return proper ERR_PTR for clk_get when !HAVE_CLK
Message-ID: <20150207164209.GA6263@katana>
References: <1423163365-15267-1-git-send-email-wsa@the-dreams.de>
 <20150205234040.GV8656@n2100.arm.linux.org.uk>
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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.
>=20
> NAK.
>=20
> 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=3D=
i2c/for-next&id=3De961a094afe04c6c8ca1adac50c8d16513f31b93


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