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

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Date:	Thu, 5 Feb 2015 23:40:40 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Wolfram Sang <wsa@...-dreams.de>
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 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.

Remember, for any clk API implementation, it is well defined that
the clk API should safely eat any struct clk that clk_get() may
return which isn't a pointer-error.

So, if an implementation returns the NULL pointer, then the clk API
functions must accept it without crashing the kernel.

Also, clock consumer drivers are _not_ allowed to dereference
struct clk.  Absolutely not permitted.

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