power: supply: olpc_battery: remove unnecessary CONFIG_PM_SLEEP
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Message ID 20201029074100.225806-1-coiby.xu@gmail.com
State New, archived
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  • power: supply: olpc_battery: remove unnecessary CONFIG_PM_SLEEP
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Commit Message

Coiby Xu Oct. 29, 2020, 7:41 a.m. UTC
SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.

Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
---
 arch/x86/platform/olpc/olpc-xo15-sci.c | 2 --
 1 file changed, 2 deletions(-)

Comments

Hans de Goede Oct. 29, 2020, 10:04 a.m. UTC | #1
Hi,

On 10/29/20 8:41 AM, Coiby Xu wrote:
> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.

No it does not, when CONFIG_PM_SLEEP is not set then the
SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses
is a no-op, so nothing will reference xo15_sci_resume leading to
a compiler warning when CONFIG_PM_SLEEP is not set.

You could drop the ifdef and add __maybe_unused to the definition
of xo15_sci_resume, but that feels like needless churn, best to
just keep this as is IMHO.

Also s/CONFIG_PM_CONFIG/CONFIG_PM_SLEEP/ in the commit message.

Regards,

Hans


> 
> Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
> ---
>  arch/x86/platform/olpc/olpc-xo15-sci.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/x86/platform/olpc/olpc-xo15-sci.c b/arch/x86/platform/olpc/olpc-xo15-sci.c
> index 85f4638764d6..716eefd735a4 100644
> --- a/arch/x86/platform/olpc/olpc-xo15-sci.c
> +++ b/arch/x86/platform/olpc/olpc-xo15-sci.c
> @@ -192,7 +192,6 @@ static int xo15_sci_remove(struct acpi_device *device)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM_SLEEP
>  static int xo15_sci_resume(struct device *dev)
>  {
>  	/* Enable all EC events */
> @@ -204,7 +203,6 @@ static int xo15_sci_resume(struct device *dev)
>  
>  	return 0;
>  }
> -#endif
>  
>  static SIMPLE_DEV_PM_OPS(xo15_sci_pm, NULL, xo15_sci_resume);
>  
>
Coiby Xu Oct. 29, 2020, 10:59 a.m. UTC | #2
Hi Hans,

Thank you for reviewing this patch!

On Thu, Oct 29, 2020 at 11:04:36AM +0100, Hans de Goede wrote:
>Hi,
>
>On 10/29/20 8:41 AM, Coiby Xu wrote:
>> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.
>
>No it does not, when CONFIG_PM_SLEEP is not set then the
>SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses
>is a no-op, so nothing will reference xo15_sci_resume leading to
>a compiler warning when CONFIG_PM_SLEEP is not set.
>
>You could drop the ifdef and add __maybe_unused to the definition
>of xo15_sci_resume, but that feels like needless churn, best to
>just keep this as is IMHO.
>

Actually, this is a tree-wide change by some semi-automation scripts.
Thank you for pointing out the issue to prevent me from releasing
another ~150 emails to flood other mailing lists.

Currently there are 929 drivers has device PM callbacks,

$ grep -rI "\.pm = &" --include=*.c  ./|wc -l
929

I put all files having device PM callbacks into four categories
based on weather a file has CONFIG_PM_SLEEP or PM macro like
SET_SYSTEM_SLEEP_PM_OPS, here are the statistics,
   1. have both CONFIG_PM_SLEEP and PM_OPS macro: 213
   2. have CONFIG_PM_SLEEP but no PM_OPS macro: 19
   3. have PM macro but not CONFIG_PM_SLEEP: 347
   4. no PM macro or CONFIG_PM_SLEEP: 302

Some drivers which have PM macro but not CONFIG_PM_SLEEP like
sound/x86/intel_hdmi_audio.c indeed use __maybe_unused to eliminate
the compiling warning. In 2011, there's a patch proposing to remove
ONFIG_PM altogether but an objection was turning CONFIG_PM on would
increase the kernel size [1]. So __maybe_unused also have this issue.
(I made a mistake when I thought PM macros like SIMPLE_DEV_PM_OPS
didn't have this issue). What do you think? Btw, It's easy for me to
add CONFIG_PM_SLEEP for those drivers have PM macro but not
CONFIG_PM_SLEEP since I have already written the necessary automation
scripts.

[1] https://lists.linux-foundation.org/pipermail/linux-pm/2011-February/030215.html

>Also s/CONFIG_PM_CONFIG/CONFIG_PM_SLEEP/ in the commit message.
>

Thank you for pointing out the typo. I've written some scripts to
automate the whole process from changing code to submitting patches.
Somehow there is still this issue.

>Regards,
>
>Hans
>
>
>>
>> Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
>> ---
>>  arch/x86/platform/olpc/olpc-xo15-sci.c | 2 --
>>  1 file changed, 2 deletions(-)
>>
>> diff --git a/arch/x86/platform/olpc/olpc-xo15-sci.c b/arch/x86/platform/olpc/olpc-xo15-sci.c
>> index 85f4638764d6..716eefd735a4 100644
>> --- a/arch/x86/platform/olpc/olpc-xo15-sci.c
>> +++ b/arch/x86/platform/olpc/olpc-xo15-sci.c
>> @@ -192,7 +192,6 @@ static int xo15_sci_remove(struct acpi_device *device)
>>  	return 0;
>>  }
>>
>> -#ifdef CONFIG_PM_SLEEP
>>  static int xo15_sci_resume(struct device *dev)
>>  {
>>  	/* Enable all EC events */
>> @@ -204,7 +203,6 @@ static int xo15_sci_resume(struct device *dev)
>>
>>  	return 0;
>>  }
>> -#endif
>>
>>  static SIMPLE_DEV_PM_OPS(xo15_sci_pm, NULL, xo15_sci_resume);
>>
>>
>

--
Best regards,
Coiby
Hans de Goede Oct. 29, 2020, 11:09 a.m. UTC | #3
Hi,

On 10/29/20 11:59 AM, Coiby Xu wrote:
> Hi Hans,
> 
> Thank you for reviewing this patch!
> 
> On Thu, Oct 29, 2020 at 11:04:36AM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 10/29/20 8:41 AM, Coiby Xu wrote:
>>> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.
>>
>> No it does not, when CONFIG_PM_SLEEP is not set then the
>> SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses
>> is a no-op, so nothing will reference xo15_sci_resume leading to
>> a compiler warning when CONFIG_PM_SLEEP is not set.
>>
>> You could drop the ifdef and add __maybe_unused to the definition
>> of xo15_sci_resume, but that feels like needless churn, best to
>> just keep this as is IMHO.
>>
> 
> Actually, this is a tree-wide change by some semi-automation scripts.
> Thank you for pointing out the issue to prevent me from releasing
> another ~150 emails to flood other mailing lists.
> 
> Currently there are 929 drivers has device PM callbacks,
> 
> $ grep -rI "\.pm = &" --include=*.c  ./|wc -l
> 929
> 
> I put all files having device PM callbacks into four categories
> based on weather a file has CONFIG_PM_SLEEP or PM macro like
> SET_SYSTEM_SLEEP_PM_OPS, here are the statistics,
>   1. have both CONFIG_PM_SLEEP and PM_OPS macro: 213
>   2. have CONFIG_PM_SLEEP but no PM_OPS macro: 19
>   3. have PM macro but not CONFIG_PM_SLEEP: 347
>   4. no PM macro or CONFIG_PM_SLEEP: 302
> 
> Some drivers which have PM macro but not CONFIG_PM_SLEEP like
> sound/x86/intel_hdmi_audio.c indeed use __maybe_unused to eliminate
> the compiling warning. In 2011, there's a patch proposing to remove
> ONFIG_PM altogether but an objection was turning CONFIG_PM on would
> increase the kernel size [1]. So __maybe_unused also have this issue.

I would expect the compiler to remove the unused function, it knows
it is unused, that is why __maybe_unused is necessary to suppress
the warning and compilers are pretty smart and agressive wrt remove
unnecessary code these days.

Regards,

Hans




>>> ---
>>>  arch/x86/platform/olpc/olpc-xo15-sci.c | 2 --
>>>  1 file changed, 2 deletions(-)
>>>
>>> diff --git a/arch/x86/platform/olpc/olpc-xo15-sci.c b/arch/x86/platform/olpc/olpc-xo15-sci.c
>>> index 85f4638764d6..716eefd735a4 100644
>>> --- a/arch/x86/platform/olpc/olpc-xo15-sci.c
>>> +++ b/arch/x86/platform/olpc/olpc-xo15-sci.c
>>> @@ -192,7 +192,6 @@ static int xo15_sci_remove(struct acpi_device *device)
>>>      return 0;
>>>  }
>>>
>>> -#ifdef CONFIG_PM_SLEEP
>>>  static int xo15_sci_resume(struct device *dev)
>>>  {
>>>      /* Enable all EC events */
>>> @@ -204,7 +203,6 @@ static int xo15_sci_resume(struct device *dev)
>>>
>>>      return 0;
>>>  }
>>> -#endif
>>>
>>>  static SIMPLE_DEV_PM_OPS(xo15_sci_pm, NULL, xo15_sci_resume);
>>>
>>>
>>
> 
> -- 
> Best regards,
> Coiby
>
Coiby Xu Oct. 29, 2020, 2:16 p.m. UTC | #4
On Thu, Oct 29, 2020 at 12:09:23PM +0100, Hans de Goede wrote:
>Hi,
>
>On 10/29/20 11:59 AM, Coiby Xu wrote:
>> Hi Hans,
>>
>> Thank you for reviewing this patch!
>>
>> On Thu, Oct 29, 2020 at 11:04:36AM +0100, Hans de Goede wrote:
>>> Hi,
>>>
>>> On 10/29/20 8:41 AM, Coiby Xu wrote:
>>>> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.
>>>
>>> No it does not, when CONFIG_PM_SLEEP is not set then the
>>> SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses
>>> is a no-op, so nothing will reference xo15_sci_resume leading to
>>> a compiler warning when CONFIG_PM_SLEEP is not set.
>>>
>>> You could drop the ifdef and add __maybe_unused to the definition
>>> of xo15_sci_resume, but that feels like needless churn, best to
>>> just keep this as is IMHO.
>>>
>>
>> Actually, this is a tree-wide change by some semi-automation scripts.
>> Thank you for pointing out the issue to prevent me from releasing
>> another ~150 emails to flood other mailing lists.
>>
>> Currently there are 929 drivers has device PM callbacks,
>>
>> $ grep -rI "\.pm = &" --include=*.c  ./|wc -l
>> 929
>>
>> I put all files having device PM callbacks into four categories
>> based on weather a file has CONFIG_PM_SLEEP or PM macro like
>> SET_SYSTEM_SLEEP_PM_OPS, here are the statistics,
>>   1. have both CONFIG_PM_SLEEP and PM_OPS macro: 213
>>   2. have CONFIG_PM_SLEEP but no PM_OPS macro: 19
>>   3. have PM macro but not CONFIG_PM_SLEEP: 347
>>   4. no PM macro or CONFIG_PM_SLEEP: 302
>>
>> Some drivers which have PM macro but not CONFIG_PM_SLEEP like
>> sound/x86/intel_hdmi_audio.c indeed use __maybe_unused to eliminate
>> the compiling warning. In 2011, there's a patch proposing to remove
>> ONFIG_PM altogether but an objection was turning CONFIG_PM on would
>> increase the kernel size [1]. So __maybe_unused also have this issue.
>
>I would expect the compiler to remove the unused function, it knows
>it is unused, that is why __maybe_unused is necessary to suppress
>the warning and compilers are pretty smart and agressive wrt remove
>unnecessary code these days.
>
Then __maybe_unused is a good solution and there's also convincing
reason to prefer __maybe_unused over CONFIG_PM_SLEEP according to
Arnd Bergmann [2],

> > By and large, drivers handle this by using a CONFIG_PM_SLEEP ifdef.
> >
> > Unless you can make an extremely convincing argument why not to do
> > so here, I'd like you to handle it that way instead.
>
> [adding linux-pm to Cc]
>
> The main reason is that everyone gets the #ifdef wrong, I run into
> half a dozen new build regressions with linux-next every week on
> average, the typical problems being:
>
> - testing CONFIG_PM_SLEEP instead of CONFIG_PM, leading to an unused
>   function warning
> - testing CONFIG_PM instead of CONFIG_PM_SLEEP, leading to a build
>   failure
> - calling a function outside of the #ifdef only from inside an
>   otherwise correct #ifdef, again leading to an unused function
>   warning
> - causing a warning inside of the #ifdef but only testing if that
>   is disabled, leading to a problem if the macro is set (this is
>   rare these days for CONFIG_PM as that is normally enabled)
>
> Using __maybe_unused avoids all of the above.

>Regards,
>
>Hans
>

[2] https://lore.kernel.org/patchwork/comment/919944/

--
Best regards,
Coiby
Hans de Goede Oct. 29, 2020, 4:03 p.m. UTC | #5
Hi,

On 10/29/20 3:16 PM, Coiby Xu wrote:
> On Thu, Oct 29, 2020 at 12:09:23PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 10/29/20 11:59 AM, Coiby Xu wrote:
>>> Hi Hans,
>>>
>>> Thank you for reviewing this patch!
>>>
>>> On Thu, Oct 29, 2020 at 11:04:36AM +0100, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 10/29/20 8:41 AM, Coiby Xu wrote:
>>>>> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG.
>>>>
>>>> No it does not, when CONFIG_PM_SLEEP is not set then the
>>>> SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses
>>>> is a no-op, so nothing will reference xo15_sci_resume leading to
>>>> a compiler warning when CONFIG_PM_SLEEP is not set.
>>>>
>>>> You could drop the ifdef and add __maybe_unused to the definition
>>>> of xo15_sci_resume, but that feels like needless churn, best to
>>>> just keep this as is IMHO.
>>>>
>>>
>>> Actually, this is a tree-wide change by some semi-automation scripts.
>>> Thank you for pointing out the issue to prevent me from releasing
>>> another ~150 emails to flood other mailing lists.
>>>
>>> Currently there are 929 drivers has device PM callbacks,
>>>
>>> $ grep -rI "\.pm = &" --include=*.c  ./|wc -l
>>> 929
>>>
>>> I put all files having device PM callbacks into four categories
>>> based on weather a file has CONFIG_PM_SLEEP or PM macro like
>>> SET_SYSTEM_SLEEP_PM_OPS, here are the statistics,
>>>   1. have both CONFIG_PM_SLEEP and PM_OPS macro: 213
>>>   2. have CONFIG_PM_SLEEP but no PM_OPS macro: 19
>>>   3. have PM macro but not CONFIG_PM_SLEEP: 347
>>>   4. no PM macro or CONFIG_PM_SLEEP: 302
>>>
>>> Some drivers which have PM macro but not CONFIG_PM_SLEEP like
>>> sound/x86/intel_hdmi_audio.c indeed use __maybe_unused to eliminate
>>> the compiling warning. In 2011, there's a patch proposing to remove
>>> ONFIG_PM altogether but an objection was turning CONFIG_PM on would
>>> increase the kernel size [1]. So __maybe_unused also have this issue.
>>
>> I would expect the compiler to remove the unused function, it knows
>> it is unused, that is why __maybe_unused is necessary to suppress
>> the warning and compilers are pretty smart and agressive wrt remove
>> unnecessary code these days.
>>
> Then __maybe_unused is a good solution and there's also convincing
> reason to prefer __maybe_unused over CONFIG_PM_SLEEP according to
> Arnd Bergmann [2],

Ok, I would be happy to merge a patch for this which drops the #ifdef-s
and adds a __maybe_unused.

Regards,

Hans

Patch
diff mbox series

diff --git a/arch/x86/platform/olpc/olpc-xo15-sci.c b/arch/x86/platform/olpc/olpc-xo15-sci.c
index 85f4638764d6..716eefd735a4 100644
--- a/arch/x86/platform/olpc/olpc-xo15-sci.c
+++ b/arch/x86/platform/olpc/olpc-xo15-sci.c
@@ -192,7 +192,6 @@  static int xo15_sci_remove(struct acpi_device *device)
 	return 0;
 }
 
-#ifdef CONFIG_PM_SLEEP
 static int xo15_sci_resume(struct device *dev)
 {
 	/* Enable all EC events */
@@ -204,7 +203,6 @@  static int xo15_sci_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
 static SIMPLE_DEV_PM_OPS(xo15_sci_pm, NULL, xo15_sci_resume);