Re: [PATCH 2/2] rust: device: implement Device::as_bound()

[Danilo Krummrich <dakr@kernel.org>]

On 7/14/25 3:24 PM, Greg KH wrote:
> On Mon, Jul 14, 2025 at 11:49:44AM +0200, Danilo Krummrich wrote:
>> On Mon Jul 14, 2025 at 7:30 AM CEST, Greg KH wrote:
>>> On Sun, Jul 13, 2025 at 08:26:54PM +0200, Danilo Krummrich wrote:
>>>> Provide an unsafe functions for abstractions to convert a regular
>>>> &Device to a &Device<Bound>.
>>>>
>>>> This is useful for registrations that provide certain guarantees for the
>>>> scope of their callbacks, such as IRQs or certain class device
>>>> registrations (e.g. PWM, miscdevice).
>>>
>>> Do we have an example where this can be used today in the tree, or is
>>> this only for new stuff going forward that would use it?
>>
>> There's miscdevice in tree, but to be fair, miscdevice doesn't need it without
>> my patch series [1] adding driver support for the existing miscdevice
>> abstractions; the patch in [2] out of this series would use it within
>> args_from_registration().
>>
>> The PWM abstractions [3] need it in bound_parent_device(). The use-case is the
>> same as everywhere else, PWM chips never out-live driver unbind, hence they can
>> provide the corresponding bus device as &Device<Bound>.
>>
>> The same is true for IRQ registrations [4]. free_irq() is guaranteed to be
>> called before driver unbind, hence we can provide a &Device<Bound> in the IRQ
>> callbacks.
>>
>> Ultimately, we want to provide this "cookie" in any driver scope that can be
>> proven to be lifetime wise limited to device / driver unbind, so there'll be
>> much more users.
> 
> Ok, so we should probably merge it now for 6.17-rc1, no objection from
> me!

Yup, gonna pick it up soon (with the casts fixed up as noted in a previous
reply). :)