Re: [PATCH 1/3] driver core: class: add class_pseudo_register

[Heiner Kallweit <hkallweit1@gmail.com>]

On 04.12.2024 19:17, Greg Kroah-Hartman wrote:
> On Wed, Dec 04, 2024 at 06:04:32PM +0100, Heiner Kallweit wrote:
>> On 04.12.2024 10:33, Greg Kroah-Hartman wrote:
>>> On Tue, Dec 03, 2024 at 09:10:05PM +0100, Heiner Kallweit wrote:
>>>> In preparation of removing class_compat support, add a helper for
>>>> creating a pseudo class in sysfs. This way we can keep class_kset
>>>> private to driver core. This helper will be used by vfio/mdev,
>>>> replacing the call to class_compat_create().
>>>>
>>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>>> ---
>>>>  drivers/base/class.c         | 14 ++++++++++++++
>>>>  include/linux/device/class.h |  1 +
>>>>  2 files changed, 15 insertions(+)
>>>>
>>>> diff --git a/drivers/base/class.c b/drivers/base/class.c
>>>> index 582b5a02a..f812236e2 100644
>>>> --- a/drivers/base/class.c
>>>> +++ b/drivers/base/class.c
>>>> @@ -578,6 +578,20 @@ struct class_compat *class_compat_register(const char *name)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(class_compat_register);
>>>>  
>>>> +/**
>>>> + * class_pseudo_register - create a pseudo class entry in sysfs
>>>> + * @name: the name of the child
>>>> + *
>>>> + * Helper for creating a pseudo class in sysfs, keeps class_kset private
>>>> + *
>>>> + * Returns: the created kobject
>>>> + */
>>>> +struct kobject *class_pseudo_register(const char *name)
>>>> +{
>>>> +	return kobject_create_and_add(name, &class_kset->kobj);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(class_pseudo_register);
>>>
>>> I see the goal here, but let's not continue on and create fake kobjects
>>> in places where there should NOT be any kobjects.  Also, you might get
>>> in trouble when removing this kobject as it thinks it is a 'struct
>>> class' but yet it isn't, right?  Did you test that?
>>>
>>
>> It's removed using kobject_put(), same as what class_compat_unregister() does.
>> I only compile-tested the changes.
> 
> I would not be able to take these unless someone actually runs them as
> the kobject removal here might be getting confused a bit.
> 
Understood. Maybe Alex/Kirti can test.

> thanks,
> 
> greg k-h