linux-kernel - Re: [PATCH] PM / OPP: pass cpumask by reference

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Message-ID: <20160501100145.GF14243@amd>
Date:	Sun, 1 May 2016 12:01:45 +0200
From:	Pavel Machek <pavel@....cz>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Viresh Kumar <vireshk@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / OPP: pass cpumask by reference

On Sat 2016-04-30 13:33:29, Arnd Bergmann wrote:
> The new use of dev_pm_opp_set_sharing_cpus resulted in a harmless compiler
> warning with CONFIG_CPUMASK_OFFSTACK=y:
> 
> drivers/cpufreq/mvebu-cpufreq.c: In function 'armada_xp_pmsu_cpufreq_init':
> include/linux/cpumask.h:550:25: error: passing argument 2 of 'dev_pm_opp_set_sharing_cpus' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
> 
> The problem here is that cpumask_var_t gets passed by reference, but
> by declaring a 'const cpumask_var_t' argument, only the pointer is
> constant, not the actual mask. This is harmless because the function
> does not actually modify the mask.
> 
> This patch changes the function prototypes for all of the related functions
> to pass a 'struct cpumask *' instead of 'cpumask_var_t', matching what
> most other such functions do in the kernel. This lets us mark all the
> other similar functions as taking a 'const' mask where possible,
> and it avoids the warning without any change in object code.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: 947bd567f7a5 ("mvebu: Use dev_pm_opp_set_sharing_cpus() to
mark OPP tables as shared")

Acked-by: Pavel Machek <pavel@....cz>

(Hiding pointer into cpumask_var_t looks wrong to me, regardless of
const issues).


-- 
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