[PATCH v4 0/1] ACPI: processor: Fix function declaration of processor_idle.c

[PATCH v4 0/1] ACPI: processor: Fix function declaration of processor_idle.c

[Huisong Li]

This serises is aimed to fix the function declaration of processor_idle.c.
And the modification idea of this series is from the link[1].
Except for this patch, all other patches in this series have been merged.

[1] https://lore.kernel.org/oe-kbuild-all/202508300519.tZQHY6HA-lkp@intel.com/

---
 Changelog
  v4:
   - remove other patches merged.
   - add static for global variable as Rafael suggested.

  v3:
   - remove the merged patch which fixed the warning in link[1]
   - add a separate patch to handle the "extern struct
     cpuidle_driver acpi_idle_driver" in processor.h.
     https://patchwork.kernel.org/project/linux-acpi/cover/20250728070612.1260859-1-lihuisong@huawei.com/
  v2:
   - split patch v1
     https://patchwork.kernel.org/project/linux-acpi/cover/20250905081900.663869-1-lihuisong@huawei.com/

Huisong Li (1):
  ACPI: processor: Do not expose the global acpi_idle_driver variable

 drivers/acpi/processor_driver.c |  3 +--
 drivers/acpi/processor_idle.c   | 12 +++++++++++-
 include/acpi/processor.h        |  1 -
 3 files changed, 12 insertions(+), 4 deletions(-)

-- 
2.33.0

[PATCH v4 1/1] ACPI: processor: Do not expose the global acpi_idle_driver variable

[Huisong Li]

Currently, processor_driver just use the global acpi_idle_driver variable
to check if the cpuidle driver is acpi_idle_driver. Actually, there is no
need to expose this global variable defined in processor_idle.c to outside.
So move the related check to acpi_processor_power_init() and limit the
global variable to a static one.

Signed-off-by: Huisong Li <lihuisong@huawei.com>
---
 drivers/acpi/processor_driver.c |  3 +--
 drivers/acpi/processor_idle.c   | 12 +++++++++++-
 include/acpi/processor.h        |  1 -
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index de17c1412678..5d824435b26b 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -166,8 +166,7 @@ static int __acpi_processor_start(struct acpi_device *device)
 	if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
 		dev_dbg(&device->dev, "CPPC data invalid or not present\n");
 
-	if (cpuidle_get_driver() == &acpi_idle_driver)
-		acpi_processor_power_init(pr);
+	acpi_processor_power_init(pr);
 
 	acpi_pss_perf_init(pr);
 
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 698d14c19587..42948495f4f1 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -51,7 +51,7 @@ module_param(latency_factor, uint, 0644);
 
 static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);
 
-struct cpuidle_driver acpi_idle_driver = {
+static struct cpuidle_driver acpi_idle_driver = {
 	.name =		"acpi_idle",
 	.owner =	THIS_MODULE,
 };
@@ -1402,8 +1402,18 @@ void acpi_processor_unregister_idle_driver(void)
 
 void acpi_processor_power_init(struct acpi_processor *pr)
 {
+	struct cpuidle_driver *drv = cpuidle_get_driver();
 	struct cpuidle_device *dev;
 
+	/*
+	 * Normally, the ACPI idle driver has already been registered before
+	 * CPU online. But the 'drv' may be NULL if register idle driver failed.
+	 * So do not anything if the idle driver isn't acpi_idle_driver or the
+	 * 'drv' is NULL.
+	 */
+	if (drv != &acpi_idle_driver)
+		return;
+
 	if (disabled_by_idle_boot_param())
 		return;
 
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 24fdaa3c2899..7146a8e9e9c2 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -417,7 +417,6 @@ static inline void acpi_processor_throttling_init(void) {}
 #endif	/* CONFIG_ACPI_CPU_FREQ_PSS */
 
 /* in processor_idle.c */
-extern struct cpuidle_driver acpi_idle_driver;
 #ifdef CONFIG_ACPI_PROCESSOR_IDLE
 void acpi_processor_power_init(struct acpi_processor *pr);
 void acpi_processor_power_exit(struct acpi_processor *pr);
-- 
2.33.0

Re: [PATCH v4 1/1] ACPI: processor: Do not expose the global acpi_idle_driver variable

[Rafael J. Wysocki]

On Mon, Sep 22, 2025 at 9:04 AM Huisong Li <lihuisong@huawei.com> wrote:
>
> Currently, processor_driver just use the global acpi_idle_driver variable
> to check if the cpuidle driver is acpi_idle_driver. Actually, there is no
> need to expose this global variable defined in processor_idle.c to outside.
> So move the related check to acpi_processor_power_init() and limit the
> global variable to a static one.
>
> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> ---
>  drivers/acpi/processor_driver.c |  3 +--
>  drivers/acpi/processor_idle.c   | 12 +++++++++++-
>  include/acpi/processor.h        |  1 -
>  3 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index de17c1412678..5d824435b26b 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -166,8 +166,7 @@ static int __acpi_processor_start(struct acpi_device *device)
>         if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
>                 dev_dbg(&device->dev, "CPPC data invalid or not present\n");
>
> -       if (cpuidle_get_driver() == &acpi_idle_driver)
> -               acpi_processor_power_init(pr);
> +       acpi_processor_power_init(pr);
>
>         acpi_pss_perf_init(pr);
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 698d14c19587..42948495f4f1 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -51,7 +51,7 @@ module_param(latency_factor, uint, 0644);
>
>  static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);
>
> -struct cpuidle_driver acpi_idle_driver = {
> +static struct cpuidle_driver acpi_idle_driver = {
>         .name =         "acpi_idle",
>         .owner =        THIS_MODULE,
>  };
> @@ -1402,8 +1402,18 @@ void acpi_processor_unregister_idle_driver(void)
>
>  void acpi_processor_power_init(struct acpi_processor *pr)
>  {
> +       struct cpuidle_driver *drv = cpuidle_get_driver();

This variable is not needed any more.

>         struct cpuidle_device *dev;
>
> +       /*
> +        * Normally, the ACPI idle driver has already been registered before
> +        * CPU online. But the 'drv' may be NULL if register idle driver failed.
> +        * So do not anything if the idle driver isn't acpi_idle_driver or the
> +        * 'drv' is NULL.

And this comment can be much shorter, maybe something like "The code
below only works if acpi_idle_driver is the current cpuidle driver."

> +        */
> +       if (drv != &acpi_idle_driver)
> +               return;
> +
>         if (disabled_by_idle_boot_param())
>                 return;
>
> diff --git a/include/acpi/processor.h b/include/acpi/processor.h
> index 24fdaa3c2899..7146a8e9e9c2 100644
> --- a/include/acpi/processor.h
> +++ b/include/acpi/processor.h
> @@ -417,7 +417,6 @@ static inline void acpi_processor_throttling_init(void) {}
>  #endif /* CONFIG_ACPI_CPU_FREQ_PSS */
>
>  /* in processor_idle.c */
> -extern struct cpuidle_driver acpi_idle_driver;
>  #ifdef CONFIG_ACPI_PROCESSOR_IDLE
>  void acpi_processor_power_init(struct acpi_processor *pr);
>  void acpi_processor_power_exit(struct acpi_processor *pr);
> --
> 2.33.0
>

Re: [PATCH v4 1/1] ACPI: processor: Do not expose the global acpi_idle_driver variable

[lihuisong (C)]

在 2025/9/23 1:38, Rafael J. Wysocki 写道:
> On Mon, Sep 22, 2025 at 9:04 AM Huisong Li <lihuisong@huawei.com> wrote:
>> Currently, processor_driver just use the global acpi_idle_driver variable
>> to check if the cpuidle driver is acpi_idle_driver. Actually, there is no
>> need to expose this global variable defined in processor_idle.c to outside.
>> So move the related check to acpi_processor_power_init() and limit the
>> global variable to a static one.
>>
>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
>> ---
>>   drivers/acpi/processor_driver.c |  3 +--
>>   drivers/acpi/processor_idle.c   | 12 +++++++++++-
>>   include/acpi/processor.h        |  1 -
>>   3 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
>> index de17c1412678..5d824435b26b 100644
>> --- a/drivers/acpi/processor_driver.c
>> +++ b/drivers/acpi/processor_driver.c
>> @@ -166,8 +166,7 @@ static int __acpi_processor_start(struct acpi_device *device)
>>          if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
>>                  dev_dbg(&device->dev, "CPPC data invalid or not present\n");
>>
>> -       if (cpuidle_get_driver() == &acpi_idle_driver)
>> -               acpi_processor_power_init(pr);
>> +       acpi_processor_power_init(pr);
>>
>>          acpi_pss_perf_init(pr);
>>
>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>> index 698d14c19587..42948495f4f1 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -51,7 +51,7 @@ module_param(latency_factor, uint, 0644);
>>
>>   static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);
>>
>> -struct cpuidle_driver acpi_idle_driver = {
>> +static struct cpuidle_driver acpi_idle_driver = {
>>          .name =         "acpi_idle",
>>          .owner =        THIS_MODULE,
>>   };
>> @@ -1402,8 +1402,18 @@ void acpi_processor_unregister_idle_driver(void)
>>
>>   void acpi_processor_power_init(struct acpi_processor *pr)
>>   {
>> +       struct cpuidle_driver *drv = cpuidle_get_driver();
> This variable is not needed any more.
Ack
>
>>          struct cpuidle_device *dev;
>>
>> +       /*
>> +        * Normally, the ACPI idle driver has already been registered before
>> +        * CPU online. But the 'drv' may be NULL if register idle driver failed.
>> +        * So do not anything if the idle driver isn't acpi_idle_driver or the
>> +        * 'drv' is NULL.
> And this comment can be much shorter, maybe something like "The code
> below only works if acpi_idle_driver is the current cpuidle driver."
will fix it.
>
>> +        */
>> +       if (drv != &acpi_idle_driver)
>> +               return;
>> +
>>          if (disabled_by_idle_boot_param())
>>                  return;
>>
>> diff --git a/include/acpi/processor.h b/include/acpi/processor.h
>> index 24fdaa3c2899..7146a8e9e9c2 100644
>> --- a/include/acpi/processor.h
>> +++ b/include/acpi/processor.h
>> @@ -417,7 +417,6 @@ static inline void acpi_processor_throttling_init(void) {}
>>   #endif /* CONFIG_ACPI_CPU_FREQ_PSS */
>>
>>   /* in processor_idle.c */
>> -extern struct cpuidle_driver acpi_idle_driver;
>>   #ifdef CONFIG_ACPI_PROCESSOR_IDLE
>>   void acpi_processor_power_init(struct acpi_processor *pr);
>>   void acpi_processor_power_exit(struct acpi_processor *pr);
>> --
>> 2.33.0
>>