linux-kernel - Re: [PATCH] power: supply: sysfs: constify the struct device

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Date: Wed, 21 Feb 2024 21:46:11 +0100
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: "Ricardo B. Marliere" <ricardo@...liere.net>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] power: supply: sysfs: constify the struct device_type
 usage

Hi,

On Tue, Feb 20, 2024 at 03:40:06PM -0300, Ricardo B. Marliere wrote:
> Since commit aed65af1cc2f ("drivers: make device_type const"), the driver
> core can properly handle constant struct device_type. Move the
> power_supply_dev_type variable to be a constant structure as well, placing
> it into read-only memory which can not be modified at runtime.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Ricardo B. Marliere <ricardo@...liere.net>
> ---
>  drivers/power/supply/power_supply.h       | 4 ++--
>  drivers/power/supply/power_supply_core.c  | 2 +-
>  drivers/power/supply/power_supply_sysfs.c | 9 ++++++---
>  3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/power/supply/power_supply.h b/drivers/power/supply/power_supply.h
> index 645eee4d6b6a..d547dbe5676f 100644
> --- a/drivers/power/supply/power_supply.h
> +++ b/drivers/power/supply/power_supply.h
> @@ -15,12 +15,12 @@ struct power_supply;
>  
>  #ifdef CONFIG_SYSFS
>  
> -extern void power_supply_init_attrs(struct device_type *dev_type);
> +extern void power_supply_init_attrs(const struct device_type *dev_type);
>  extern int power_supply_uevent(const struct device *dev, struct kobj_uevent_env *env);
>  
>  #else
>  
> -static inline void power_supply_init_attrs(struct device_type *dev_type) {}
> +static inline void power_supply_init_attrs(const struct device_type *dev_type) {}
>  #define power_supply_uevent NULL
>  
>  #endif /* CONFIG_SYSFS */
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index ecef35ac3b7e..fda21cf4111c 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(power_supply_class);
>  
>  static BLOCKING_NOTIFIER_HEAD(power_supply_notifier);
>  
> -static struct device_type power_supply_dev_type;
> +static const struct device_type power_supply_dev_type;

This creates an empty struct, which is being used in this file...

>  
>  #define POWER_SUPPLY_DEFERRED_REGISTER_TIME	msecs_to_jiffies(10)
>  
> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
> index 977611e16373..ed365ca54c90 100644
> --- a/drivers/power/supply/power_supply_sysfs.c
> +++ b/drivers/power/supply/power_supply_sysfs.c
> @@ -399,12 +399,15 @@ static const struct attribute_group *power_supply_attr_groups[] = {
>  	NULL,
>  };
>  
> -void power_supply_init_attrs(struct device_type *dev_type)
> +static const struct device_type power_supply_dev_type = {
> +	.name = "power_supply",
> +	.groups = power_supply_attr_groups,
> +};

... and this creates the correct one in power_supply_sysfs.c, but it
is not being used at all. Maybe get some sleep and/or read again
what 'static' means for a global variable?

> +void power_supply_init_attrs(const struct device_type *dev_type)
>  {

This function no longer uses dev_type argument, so you can remove
it.

-- Sebastian

>  	int i;
>  
> -	dev_type->groups = power_supply_attr_groups;
> -

>  	for (i = 0; i < ARRAY_SIZE(power_supply_attrs); i++) {
>  		struct device_attribute *attr;
>  
> 
> ---
> base-commit: a9b254892ce1a447b06c5019cbf0e9caeb48c138
> change-id: 20240220-device_cleanup-power-037594022cb1
> 
> Best regards,
> -- 
> Ricardo B. Marliere <ricardo@...liere.net>
> 

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