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

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Date:   Wed, 11 Jan 2023 13:14:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Hans de Goede <hdegoede@...hat.com>
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()

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.

thanks,

greg k-h