linux-kernel - Re: [PATCH] iio: health/afe4403: mark suspend/resume functions __maybe

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Date:	Wed, 17 Feb 2016 19:35:47 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>,
	Daniel Baluta <daniel.baluta@...il.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	"Andrew F . Davis" <afd@...com>, Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: health/afe4403: mark suspend/resume functions
 __maybe_unused

On 15/02/16 09:20, Arnd Bergmann wrote:
> On Monday 15 February 2016 11:18:20 Daniel Baluta wrote:
>> On Mon, Feb 15, 2016 at 11:02 AM, Arnd Bergmann <arnd@...db.de> wrote:
>>> The newly added afe4403 driver implements suspend/resume using the
>>> SIMPLE_DEV_PM_OPS() macro, which leaves out references to the actual
>>> functions when CONFIG_PM is disabled, causing a harmless warning:
>>>
>>> health/afe4403.c:509:12: error: 'afe4403_suspend' defined but not used
>>> health/afe4403.c:530:12: error: 'afe4403_resume' defined but not used
>>>
>>> This marks the functions as __maybe_unused so we don't get those
>>> warnings.
>>>
>> Or we could put _suspend and _resume under CONFIG_PM_SLEEP.
> 
> That never works reliably. I still have a backlog of ~50 patches
> of drivers that got this wrong in the past.
> 
>> We have:
>>
>> :~/w/iio/drivers/iio$ ack-grep SIMPLE_DEV_PM_OPS | wc -l
>> 31
>>
>> and only 2 drivers using __maybe_unused.
>>
>> :~/w/iio/drivers/iio$ ack-grep maybe_unused
>> gyro/itg3200_core.c
>> 354:static int __maybe_unused itg3200_suspend(struct device *dev)
>> 365:static int __maybe_unused itg3200_resume(struct device *dev)
>>
>> adc/imx7d_adc.c
>> 553:static int __maybe_unused imx7d_adc_suspend(struct device *dev)
>> 566:static int __maybe_unused imx7d_adc_resume(struct device *dev)
>>
>> For consistency, we should use CONFIG_PM_SLEEP and get rid of __maybe_unused.
> 
> I hope to eventually kill off all the CONFIG_PM_SLEEP checks and then
> make it work automatically by redefining SIMPLE_DEV_PM_OPS so it
> leaves an unused reference to the functions.
Applied to the togreg branch of iio.git

Thanks,

Jonathan
> 
> 	Arnd
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