linux-kernel - Re: linux-next: build warnings after merge of the char-misc tree

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Date:   Mon, 14 Nov 2022 17:03:31 +0800
From:   Liu Ying <victor.liu@....com>
To:     Arnd Bergmann <arnd@...db.de>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Greg KH <greg@...ah.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-next <linux-next@...r.kernel.org>
Subject: Re: linux-next: build warnings after merge of the char-misc tree

Hi Arnd,

On Mon, 2022-11-14 at 08:33 +0100, Arnd Bergmann wrote:
> On Mon, Nov 14, 2022, at 08:17, Stephen Rothwell wrote:
> > Hi all,
> > 
> > After merging the char-misc tree, today's linux-next build (powerpc
> > allnoconfig) produced these warnings:
> > 
> > drivers/bus/simple-pm-bus.c:96:12: warning: 
> > 'simple_pm_bus_runtime_resume' defined but not used [-Wunused-function]
> >    96 | static int simple_pm_bus_runtime_resume(struct device *dev)
> >       |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/bus/simple-pm-bus.c:87:12: warning: 
> > 'simple_pm_bus_runtime_suspend' defined but not used [-Wunused-function]
> >    87 | static int simple_pm_bus_runtime_suspend(struct device *dev)
> >       |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 
> > Introduced by commit
> > 
> >   882cf4c913d7 ("drivers: bus: simple-pm-bus: Use clocks")
> 
> I see that this is caused by the patch using the old-style
> SET_RUNTIME_PM_OPS/SET_NOIRQ_SYSTEM_SLEEP_PM_OPS macros
> instead of the correct SYSTEM_SLEEP_PM_OPS/NOIRQ_SYSTEM_SLEEP_PM_OPS
> versions.
> 

You meant RUNTIME_PM_OPS/NOIRQ_SYSTEM_SLEEP_PM_OPS macros should be
used, right?

Why not add __maybe_unused to the callbacks like below snippet instead?
This way, the old-style macros may determine those callbacks are NULL
or non-NULL according to CONFIG_PM_SLEEP and CONFIG_PM.
-------------------------------8<-------------------------------------
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -84,7 +84,7 @@ static int simple_pm_bus_remove(struct
platform_device *pdev)
        return 0;
 }

-static int simple_pm_bus_runtime_suspend(struct device *dev)
+static int __maybe_unused simple_pm_bus_runtime_suspend(struct device
*dev)
 {
        struct simple_pm_bus *bus = dev_get_drvdata(dev);

@@ -93,7 +93,7 @@ static int simple_pm_bus_runtime_suspend(struct
device *dev)
        return 0;
 }

-static int simple_pm_bus_runtime_resume(struct device *dev)
+static int __maybe_unused simple_pm_bus_runtime_resume(struct device
*dev)
 {
        struct simple_pm_bus *bus = dev_get_drvdata(dev);
        int ret;
-------------------------------8<-------------------------------------

Regards,
Liu Ying