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SubjectRe: [PATCH v4 2/4] mfd: Add Samsung Exynos Low Power Audio Subsystem driver
On Wed, 10 Aug 2016, Sylwester Nawrocki wrote:

> On 08/09/2016 10:50 PM, Lee Jones wrote:
> > On Tue, 09 Aug 2016, Sylwester Nawrocki wrote:
> >
> >> > On 08/09/2016 05:05 PM, Lee Jones wrote:
> >>>> > >> +static SIMPLE_DEV_PM_OPS(lpass_pm_ops, exynos_lpass_suspend,
> >>>>> > >> > + exynos_lpass_resume);
> >>> > > Put this up by the PM functions.
> >> >
> >> > Sorry, I don't understand this comment, which PM functions do you
> >> > mean exactly?
> > *_suspend and *_resume. PM == Power Management.
> >
> > You also need to place the functions in side some CONFIG_PM_SLEEP
> > guards. Grep around, you'll see what I mean.
>
> OK, but couldn't we just leave it with that SIMPLE_DEV_PM_OPS()
> macro? It saves us an #ifdef ugliness and if I actually grep
> drivers/mfd most of the drivers use either SIMPLE_DEV_PM_OPS() or
> SET_SYSTEM_SLEEP_PM_OPS. Are you asking me to change the above to:
>
> static const struct dev_pm_ops exynos_lpass_pm_ops = {
> #ifdef CONFIG_PM_SLEEP
> .suspend = exynos_lpass_suspend,
> .resume = exynos_lpass_resume,
> .freeze = exynos_lpass_suspend,
> .thaw = exynos_lpass_resume,
> .poweroff = exynos_lpass_suspend,
> .restore = exynos_lpass_resume,
> #endif
> }
>
> or perhaps
>
> static const struct dev_pm_ops exynos_lpass_pm_ops = {
> SET_SYSTEM_SLEEP_PM_OPS(exynos_lpass_suspend, exynos_lpass_resume)
> }
>
> ?

Not like that. Grep 'drivers/mfd' for "CONFIG_PM_SLEEP" as
suggested. You will find that the actual *_suspend and *_resume
functions are guarded in order to save space.

> I agree about the CONFIG_PM_SLEEP guards. There is very little
> chance though the LPASS driver will ever be used with
> CONFIG_PM_SLEEP disabled. How about adding __maybe_unused attribute
> to the *_suspend/*_resume functions then? I can see this pattern
> used already in drivers/mfd.

It's more common practice to use CONFIG_PM_SLEEP:

$ git grep __maybe_unused -- drivers/mfd/ | wc -l
7
$ git grep CONFIG_PM_SLEEP -- drivers/mfd/ | wc -l
31

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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