Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a const *

[Maximilian Luz <luzmaximilian@gmail.com>]

Hi,

On 11/23/22 13:25, Greg Kroah-Hartman wrote:
> The uevent() callback in struct device_type should not be modifying the
> device that is passed into it, so mark it as a const * and propagate the
> function signature changes out into all relevant subsystems that use
> this callback.

[...]

> diff --git a/drivers/platform/surface/aggregator/bus.c b/drivers/platform/surface/aggregator/bus.c
> index de539938896e..407eb55050a6 100644
> --- a/drivers/platform/surface/aggregator/bus.c
> +++ b/drivers/platform/surface/aggregator/bus.c
> @@ -35,9 +35,9 @@ static struct attribute *ssam_device_attrs[] = {
>   };
>   ATTRIBUTE_GROUPS(ssam_device);
>   
> -static int ssam_device_uevent(struct device *dev, struct kobj_uevent_env *env)
> +static int ssam_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
>   {
> -	struct ssam_device *sdev = to_ssam_device(dev);
> +	const struct ssam_device *sdev = to_ssam_device(dev);
>   
>   	return add_uevent_var(env, "MODALIAS=ssam:d%02Xc%02Xt%02Xi%02Xf%02X",
>   			      sdev->uid.domain, sdev->uid.category,

[...]

> --- a/include/linux/surface_aggregator/device.h
> +++ b/include/linux/surface_aggregator/device.h
> @@ -229,7 +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)
> +static inline struct ssam_device *to_ssam_device(const struct device *d)
>   {
>   	return container_of(d, struct ssam_device, dev);
>   }

I am slightly conflicted about this change as that now more or less
implicitly drops the const. So I'm wondering if it wouldn't be better to
either create a function specifically for const pointers or to just
open-code it in the instance above.

I guess we could also convert this to a macro. Then at least there
wouldn't be an explicit and potentially misleading const-conversion
indicated in the function signature.

Regards,
Max