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

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Message-ID: <fzakqxmfrx7jh73ylxikjd2ehltqgkncfn2ks4chbncssfzch7@g6epshmmdanp>
Date: Thu, 22 Feb 2024 18:17:52 -0300
From: "Ricardo B. Marliere" <ricardo@...liere.net>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
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 Sebastian,

On 21 Feb 21:46, Sebastian Reichel wrote:
> 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?

Oh, silly me. This was a stupid patch indeed, sorry about that. I'll
send a proper fix later!

Thanks for reviewing,
-	Ricardo.


> 
> > +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>
> >