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SubjectRe: [PATCH 3/8] PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM_OPS macros
Hi Jonathan,

Le mer., janv. 5 2022 at 10:03:32 +0000, Jonathan Cameron
<Jonathan.Cameron@Huawei.com> a écrit :
> On Tue, 4 Jan 2022 21:42:09 +0000
> Paul Cercueil <paul@crapouillou.net> wrote:
>
>> These macros are defined conditionally, according to CONFIG_PM:
>> - if CONFIG_PM is enabled, these macros resolve to
>> DEFINE_SIMPLE_DEV_PM_OPS(), and the dev_pm_ops symbol will be
>> exported.
>>
>> - if CONFIG_PM is disabled, these macros will result in a dummy
>> static
>> dev_pm_ops to be created with the __maybe_unused flag. The
>> dev_pm_ops
>> will then be discarded by the compiler, along with the provided
>> callback functions if they are not used anywhere else.
>>
>> In the second case, the symbol is not exported, which should be
>> perfectly fine - users of the symbol should all use the pm_ptr() or
>> pm_sleep_ptr() macro, so the dev_pm_ops marked as "extern" in the
>> client's code will never be accessed.
>>
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> ---
>> include/linux/pm.h | 33 ++++++++++++++++++++++++++++++---
>> 1 file changed, 30 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/pm.h b/include/linux/pm.h
>> index 389e600df233..a1ce29566aea 100644
>> --- a/include/linux/pm.h
>> +++ b/include/linux/pm.h
>> @@ -8,6 +8,7 @@
>> #ifndef _LINUX_PM_H
>> #define _LINUX_PM_H
>>
>> +#include <linux/export.h>
>> #include <linux/list.h>
>> #include <linux/workqueue.h>
>> #include <linux/spinlock.h>
>> @@ -357,14 +358,40 @@ struct dev_pm_ops {
>> #define SET_RUNTIME_PM_OPS(suspend_fn, resume_fn, idle_fn)
>> #endif
>>
>> +#define _DEFINE_DEV_PM_OPS(name, \
>> + suspend_fn, resume_fn, \
>> + runtime_suspend_fn, runtime_resume_fn, idle_fn) \
>> +const struct dev_pm_ops name = { \
>> + SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
>> + RUNTIME_PM_OPS(runtime_suspend_fn, runtime_resume_fn, idle_fn) \
>> +}
>> +
>
> one blank line probably enough.
>
>> +
>> /*
>> * Use this if you want to use the same suspend and resume
>> callbacks for suspend
>> * to RAM and hibernation.
>> */
>> #define DEFINE_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
>> -const struct dev_pm_ops name = { \
>> - SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
>> -}
>> + _DEFINE_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL)
>> +
>> +#ifdef CONFIG_PM
>> +#define _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn,
>> runtime_suspend_fn, \
>> + runtime_resume_fn, idle_fn, sec) \
>> + _DEFINE_DEV_PM_OPS(name, suspend_fn, resume_fn,
>> runtime_suspend_fn, \
>> + runtime_resume_fn, idle_fn); \
>> + _EXPORT_SYMBOL(name, sec)
>> +#else
>> +#define _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn,
>> runtime_suspend_fn, \
>> + runtime_resume_fn, idle_fn, sec) \
>> +static __maybe_unused _DEFINE_DEV_PM_OPS(__static_##name,
>> suspend_fn, \
>> + resume_fn, runtime_suspend_fn, \
>> + runtime_resume_fn, idle_fn)
>> +#endif
>> +
>> +#define EXPORT_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
>> + _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL,
>> "")
>> +#define EXPORT_GPL_SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
>> + _EXPORT_DEV_PM_OPS(name, suspend_fn, resume_fn, NULL, NULL, NULL,
>> "_gpl")
>
> So you can get away with these two cases because the
> SYSTEM_SLEEP_PM_OPS() all have
> pm_sleep_ptr() wrappers. However, _EXPORT_DEV_PM_OPS() could be used
> directly and
> would require __maybe_unused for the RUNTIME_PM_OPS() parameters
> which isn't ideal.

I don't see why. On both cases (CONFIG_PM enabled/disabled) the
runtime-PM callbacks are referenced directly, so at no point do they
appear as unused; therefore __maybe_unused is not needed.

Cheers,
-Paul

> Maybe I'm missing some reason that isn't a problem though as easy to
> get lost in
> these macros. :)
>
> You could argue that the _ is meant to indicate that macro shouldn't
> be used directly
> but I'm not that optimistic.
>
> Jonathan
>
>
>
>>
>> /* Deprecated. Use DEFINE_SIMPLE_DEV_PM_OPS() instead. */
>> #define SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
>


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