linux-kernel - Re: [PATCH v2 03/16] platform/surface: aggregator: move to_ssam_device() to use container_of

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Message-ID: <4656f2a5-9a81-58b1-742e-f466fd5c5128@redhat.com>
Date:   Wed, 11 Jan 2023 13:15:43 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Maximilian Luz <luzmaximilian@...il.com>,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v2 03/16] platform/surface: aggregator: move
 to_ssam_device() to use container_of_const()

Hi,

On 1/11/23 13:14, Greg Kroah-Hartman wrote:
> On Wed, Jan 11, 2023 at 12:54:54PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 1/11/23 12:30, Greg Kroah-Hartman wrote:
>>> The driver core is changing to pass some pointers as const, so move
>>> to_ssam_device() to use container_of_const() to handle this change.
>>> to_ssam_device() now properly keeps the const-ness of the pointer passed
>>> into it, while as before it could be lost.
>>>
>>> Cc: Maximilian Luz <luzmaximilian@...il.com>
>>> Cc: platform-driver-x86@...r.kernel.org
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>> ---
>>>  include/linux/surface_aggregator/device.h | 5 +----
>>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>>
>>> diff --git a/include/linux/surface_aggregator/device.h b/include/linux/surface_aggregator/device.h
>>> index 46c45d1b6368..24151a0e2c96 100644
>>> --- a/include/linux/surface_aggregator/device.h
>>> +++ b/include/linux/surface_aggregator/device.h
>>> @@ -229,10 +229,7 @@ static inline bool is_ssam_device(struct device *d)
>>>   * Return: Returns a pointer to the &struct ssam_device wrapping the given
>>>   * device @d.
>>>   */
>>> -static inline struct ssam_device *to_ssam_device(struct device *d)
>>> -{
>>> -	return container_of(d, struct ssam_device, dev);
>>> -}
>>> +#define to_ssam_device(d)	container_of_const(d, struct ssam_device, dev)
>>
>> There is a kernel-doc comment for this helper, I'm not sure if sphinx is going
>> to like changing this from a static inline to a #define ?
>>
>> At a minimum I guess the generated docs are going to loose some type info
>> by switching to a define. Can we keep this as a static inline ?
> 
> No, container_of_const() will not work properly as an inline function as
> you don't know the return type until the preprocessor runs.  I thought
> kerneldoc should still work just fine here as it does work for defines
> in other places.

Ok then this is fine as is. Thanks for clarifying why the switch to
a #define is necessary.

Regards,

Hans