Messages in this thread | | | Date | Wed, 23 Nov 2022 14:59:00 +0100 | Subject | Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a const * | From | Maximilian Luz <> |
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On 11/23/22 14:34, Andy Shevchenko wrote: > On Wed, Nov 23, 2022 at 02:14:31PM +0100, Maximilian Luz wrote: >> 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. > > [...] > >>> -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. > > This is an intermediate step as far as I know since moving container_of to > recognize const is a bit noisy right now. I guess you can find a discussion > on the topic between Greg and Sakari.
Thanks! I assume you are referring to the following?
https://lore.kernel.org/lkml/4218173bd72b4f1899d4c41a8e251f0d@AcuMS.aculab.com/T/
As far as I can tell this is only a warning in documentation, not compile time (which would probably be impossible?).
As I've said I'd be fine with converting the function to a macro (and preferably adding a similar warning like the one proposed in that thread). The point that irks me up is just that, as proposed, the function signature would now advertise a conversion that should never be happening.
Having two separate functions would create a compile-time guarantee, so I'd prefer that, but I can understand if that might be considered too noisy in code. Or if there is a push to make container_of() emit a compile-time warning I'd also be perfectly happy with converting it to a macro now as that'd alleviate the need for functions in the future.
Regards, Max
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