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Date: Wed, 29 Oct 2025 16:30:11 +0100
Message-Id: <DDUWW90NZIDY.2TVA8S0RDSXZJ@kernel.org>
To: "Alice Ryhl" <aliceryhl@google.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH 2/8] rust: device: introduce Device::drvdata()
Cc: <gregkh@linuxfoundation.org>, <rafael@kernel.org>,
 <bhelgaas@google.com>, <kwilczynski@kernel.org>,
 <david.m.ertman@intel.com>, <ira.weiny@intel.com>, <leon@kernel.org>,
 <acourbot@nvidia.com>, <ojeda@kernel.org>, <alex.gaynor@gmail.com>,
 <boqun.feng@gmail.com>, <gary@garyguo.net>, <bjorn3_gh@protonmail.com>,
 <lossin@kernel.org>, <a.hindborg@kernel.org>, <tmgross@umich.edu>,
 <pcolberg@redhat.com>, <rust-for-linux@vger.kernel.org>,
 <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20251020223516.241050-1-dakr@kernel.org>
 <20251020223516.241050-3-dakr@kernel.org> <aQIPvaFJIXySV-Q5@google.com>
In-Reply-To: <aQIPvaFJIXySV-Q5@google.com>

On Wed Oct 29, 2025 at 1:59 PM CET, Alice Ryhl wrote:
> Are you going to open that docs PR to the Rust compiler about the size
> of TypeID that we talked about? :)

Yes, I will -- thanks for the reminder.

> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
>
>> +// Compile-time checks.
>> +const _: () =3D {
>> +    // Assert that we can `read()` / `write()` a `TypeId` instance from=
 / into `struct driver_type`.
>> +    static_assert!(core::mem::size_of::<bindings::driver_type>() =3D=3D=
 core::mem::size_of::<TypeId>());
>> +};
>
> You don't need the "const _: ()" part. See the definition of
> static_assert! to see why.

Indeed, good catch -- same for the suggestions below.

> Also, I would not require equality. The Rust team did not think that it
> would ever increase in size, but it may decrease.
>
>>  /// The core representation of a device in the kernel's driver model.
>>  ///
>>  /// This structure represents the Rust abstraction for a C `struct devi=
ce`. A [`Device`] can either
>> @@ -198,12 +204,29 @@ pub unsafe fn as_bound(&self) -> &Device<Bound> {
>>  }
>> =20
>>  impl Device<CoreInternal> {
>> +    fn type_id_store<T: 'static>(&self) {
>
> This name isn't great. How about "set_type_id()" instead?
>
> Alice=20