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Date: Fri, 01 Aug 2025 11:00:12 +0200
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Cc: <lorenzo.stoakes@oracle.com>, <vbabka@suse.cz>,
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Subject: Re: [PATCH 3/4] rust: drm: remove pin annotations from drm::Device
From: "Benno Lossin" <lossin@kernel.org>
To: "Danilo Krummrich" <dakr@kernel.org>
X-Mailer: aerc 0.20.1
References: <20250731154919.4132-1-dakr@kernel.org>
 <20250731154919.4132-4-dakr@kernel.org>
 <DBQGW0NIQJRX.MU0QD5GMFJYM@kernel.org>
 <DBQY1S7V8IIS.3NCGOZ8ALU7QG@kernel.org>
In-Reply-To: <DBQY1S7V8IIS.3NCGOZ8ALU7QG@kernel.org>

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