On Fri Oct 17, 2025 at 3:04 PM CEST, Alice Ryhl wrote:
> On Thu, Oct 16, 2025 at 02:55:28PM +0200, Danilo Krummrich wrote:
>> The driver model defines the lifetime of the private data stored in (and
>> owned by) a bus device to be valid from when the driver is bound to a
>> device (i.e. from successful probe()) until the driver is unbound from
>> the device.
>>
>> This is already taken care of by the Rust implementation of the driver
>> model. However, we still ask drivers to return a Result<Pin<KBox<Self>>>
>> from probe().
>>
>> Unlike in C, where we do not have the concept of initializers, but
>> rather deal with uninitialized memory, drivers can just return an
>> impl PinInit<Self, Error> instead.
>>
>> This contributed to more clarity to the fact that a driver returns it's
>> device private data in probe() and the Rust driver model owns the data,
>> manages the lifetime and - considering the lifetime - provides (safe)
>> accessors for the driver.
>>
>> Hence, let probe() functions return an impl PinInit<Self, Error> instead
>> of Result<Pin<KBox<Self>>>.
>>
>> Signed-off-by: Danilo Krummrich <[email protected]>
>> ---
>> Depends on a minor pin-init patch [1] (Benno will send it to the list
>> soon). A branch with this patch and the pin-init dependency is available
>> in [2].
>>
>> [1] https://github.com/Rust-for-Linux/pin-init/pull/86/commits
>> [2]
>> https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=probe_return
>
> Overall LGTM.
> Reviewed-by: Alice Ryhl <[email protected]>
Thanks!
>> impl Device<CoreInternal> {
>> /// Store a pointer to the bound driver's private data.
>> - pub fn set_drvdata(&self, data: impl ForeignOwnable) {
>> + pub fn set_drvdata<T: 'static>(&self, data: impl PinInit<T, Error>) ->
>> Result {
>> + let data = KBox::pin_init(data, GFP_KERNEL)?;
>
> Perhaps the gfp flags should be an argument set_drvdata?
There shouldn't be a need, so I'd rather do that should we find a valid case.
