linux-kernel - Re: [PATCH 01/13] clk: Add non CONFIG_HAVE

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Date:	Sat, 21 Apr 2012 13:42:19 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Viresh Kumar <viresh.linux@...il.com>
Cc:	akpm@...ux-foundation.org, mturquette@...aro.org,
	sshtylyov@...sta.com, spear-devel@...t.st.com,
	linux-kernel@...r.kernel.org, jgarzik@...hat.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 01/13] clk: Add non CONFIG_HAVE_CLK routines

On Sat, Apr 21, 2012 at 05:17:28PM +0530, Viresh Kumar wrote:
> Many drivers are shared between architectures that may or may not have HAVE_CLK
> selected for them. To remove compilation errors for them we enclose clk_*()
> calls in these drivers within #ifdef CONFIG_HAVE_CLK, #endif.

All you're doing is making drivers buildable.  Drivers will not be usable
with this (they'll error out because clk_get() will fail.)

For example:

-#ifndef CONFIG_HAVE_CLK
-/* Dummy stub for clk framework */
-#define clk_get(dev, id)       NULL
-#define clk_put(clock)         do {} while (0)
-#define clk_enable(clock)      do {} while (0)
-#define clk_disable(clock)     do {} while (0)
-#endif
-

along with your change in this patch changes the drivers behaviour.

A better solution would be to assume that if HAVE_CLK is not set, then
that means there's no control over clocks, and therefore the clk API
should become totally transparent and non-failure inducing.  So, having
clk_get() return NULL, and having all the other clk API functions ignore
their argument (just like the macros above) is the right solution here.
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