The #[pin_data] and #[pin] annotations are not necessary for
drm::Device, since we don't use any pin-init macros, but only
__pinned_init() on the impl PinInit<T::Data, Error> argument of
drm::Device::new().

Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/drm/device.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index d19410deaf6c..d0a9528121f1 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -54,10 +54,8 @@ macro_rules! drm_legacy_fields {
 ///
 /// `self.dev` is a valid instance of a `struct device`.
 #[repr(C)]
-#[pin_data]
 pub struct Device<T: drm::Driver> {
     dev: Opaque<bindings::drm_device>,
-    #[pin]
     data: T::Data,
 }
 
-- 
2.50.0

On Thu Jul 31, 2025 at 5:48 PM CEST, Danilo Krummrich wrote:
> The #[pin_data] and #[pin] annotations are not necessary for
> drm::Device, since we don't use any pin-init macros, but only
> __pinned_init() on the impl PinInit<T::Data, Error> argument of
> drm::Device::new().
>
> Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reviewed-by: Benno Lossin <lossin@kernel.org>

---
Cheers,
Benno

> ---
>  rust/kernel/drm/device.rs | 2 --
>  1 file changed, 2 deletions(-)

On Thu Jul 31, 2025 at 5:48 PM CEST, Danilo Krummrich wrote:
> The #[pin_data] and #[pin] annotations are not necessary for
> drm::Device, since we don't use any pin-init macros, but only
> __pinned_init() on the impl PinInit<T::Data, Error> argument of
> drm::Device::new().

But you're still pinning `Device`, right?

> Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/drm/device.rs | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
> index d19410deaf6c..d0a9528121f1 100644
> --- a/rust/kernel/drm/device.rs
> +++ b/rust/kernel/drm/device.rs
> @@ -54,10 +54,8 @@ macro_rules! drm_legacy_fields {
>  ///
>  /// `self.dev` is a valid instance of a `struct device`.
>  #[repr(C)]
> -#[pin_data]
>  pub struct Device<T: drm::Driver> {
>      dev: Opaque<bindings::drm_device>,
> -    #[pin]
>      data: T::Data,

Looking at this code again, I also noticed that it was wrong before this
patch: `Device<T>` implemented `Unpin` if `T::Data` did which is most
likely wrong (or is `drm_device` not address sensitive?).

So good to see that fixed, thanks!

---
Cheers,
Benno

>  }
>  

On Thu Jul 31, 2025 at 8:54 PM CEST, Benno Lossin wrote:
> On Thu Jul 31, 2025 at 5:48 PM CEST, Danilo Krummrich wrote:
>> The #[pin_data] and #[pin] annotations are not necessary for
>> drm::Device, since we don't use any pin-init macros, but only
>> __pinned_init() on the impl PinInit<T::Data, Error> argument of
>> drm::Device::new().
>
> But you're still pinning `Device`, right?

A drm::Device instance never exists other than as ARef<drm::Device>.

>> Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>> ---
>>  rust/kernel/drm/device.rs | 2 --
>>  1 file changed, 2 deletions(-)
>>
>> diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
>> index d19410deaf6c..d0a9528121f1 100644
>> --- a/rust/kernel/drm/device.rs
>> +++ b/rust/kernel/drm/device.rs
>> @@ -54,10 +54,8 @@ macro_rules! drm_legacy_fields {
>>  ///
>>  /// `self.dev` is a valid instance of a `struct device`.
>>  #[repr(C)]
>> -#[pin_data]
>>  pub struct Device<T: drm::Driver> {
>>      dev: Opaque<bindings::drm_device>,
>> -    #[pin]
>>      data: T::Data,
>
> Looking at this code again, I also noticed that it was wrong before this
> patch: `Device<T>` implemented `Unpin` if `T::Data` did which is most
> likely wrong (or is `drm_device` not address sensitive?).

It is, but as mentioned above a drm::Device only ever exists as
ARef<drm::Device>.

So, in drm::Device::new() we allocate the drm::Device with __drm_dev_alloc(),
initialize data in-place within this allocated memory and create an
ARef<drm::Device> directly from the raw pointer returned by __drm_dev_alloc().

> So good to see that fixed, thanks!
>
> ---
> Cheers,
> Benno
>
>>  }
>>  

On Fri Aug 1, 2025 at 10:21 AM CEST, Danilo Krummrich wrote:
> On Thu Jul 31, 2025 at 8:54 PM CEST, Benno Lossin wrote:
>> On Thu Jul 31, 2025 at 5:48 PM CEST, Danilo Krummrich wrote:
>>>  #[repr(C)]
>>> -#[pin_data]
>>>  pub struct Device<T: drm::Driver> {
>>>      dev: Opaque<bindings::drm_device>,
>>> -    #[pin]
>>>      data: T::Data,
>>
>> Looking at this code again, I also noticed that it was wrong before this
>> patch: `Device<T>` implemented `Unpin` if `T::Data` did which is most
>> likely wrong (or is `drm_device` not address sensitive?).
>
> It is, but as mentioned above a drm::Device only ever exists as
> ARef<drm::Device>.

Yeah the `Unpin` thing isn't a problem for `ARef`, but we are
theoretically allowed to implement moving out of an `ARef` (given that
it is unique) when the type is `Unpin`.

Thanks for confirming.

---
Cheers,
Benno