On Wed, Nov 23, 2022 at 12:25:32PM -0400, Jason Gunthorpe wrote:

On Wed, Nov 23, 2022 at 04:37:59PM +0100, Greg Kroah-Hartman wrote:

quoted

static inline struct device *__kobj_to_dev(struct kobject *kobj)
{
        return container_of(kobj, struct device, kobj);
}

static inline const struct device *__kobj_to_dev_const(const struct kobject *kobj)
{
        return container_of(kobj, const struct device, kobj);
}

/*
 * container_of() will happily take a const * and spit back a non-const * as it
 * is just doing pointer math.  But we want to be a bit more careful in the
 * driver code, so manually force any const * of a kobject to also be a const *
 * to a device.
 */
#define kobj_to_dev(kobj)                                       \
        _Generic((kobj),                                        \
                 const struct kobject *: __kobj_to_dev_const,   \
                 struct kobject *: __kobj_to_dev)(kobj)


Want me to do the same thing here as well?

It would be nice to have a shared macro code gen all of the above
instead of copy and pasting it. Then maybe other cases beyond struct
device could adopt const too..

I think I tried to create such a beast, but failed, so ended up
open-coding it in a few places in the USB headers already.  I can try it
again, but the redirection gets tricky (defines creating defines...)

thanks,

greg k-h