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Wed, 04 Jun 2025 02:42:41 -0700 (PDT) Message-ID: <311a3039-286a-49e6-b47a-75f5a173e922@gmail.com> Date: Wed, 4 Jun 2025 11:42:39 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] rust: miscdevice: add additional data to MiscDeviceRegistration To: Alice Ryhl Cc: Benno Lossin , Miguel Ojeda , Danilo Krummrich , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Trevor Gross , Arnd Bergmann , Greg Kroah-Hartman , Lee Jones , Daniel Almeida , =?UTF-8?Q?Gerald_Wisb=C3=B6ck?= , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250530-b4-rust_miscdevice_registrationdata-v4-0-d313aafd7e59@gmail.com> <20250530-b4-rust_miscdevice_registrationdata-v4-2-d313aafd7e59@gmail.com> <3eef5777-9190-4782-8433-7b6ad4b9acd3@gmail.com> Content-Language: en-US, de-DE From: Christian Schrefl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 04.06.25 11:40 AM, Alice Ryhl wrote: > On Mon, Jun 02, 2025 at 11:16:33PM +0200, Christian Schrefl wrote: >> On 31.05.25 2:23 PM, Benno Lossin wrote: >>> On Fri May 30, 2025 at 10:46 PM CEST, Christian Schrefl wrote: >>>> + unsafe { core::ptr::drop_in_place(self.data.get()) }; >>>> } >>>> } >>>> >>>> @@ -109,6 +135,13 @@ pub trait MiscDevice: Sized { >>>> /// What kind of pointer should `Self` be wrapped in. >>>> type Ptr: ForeignOwnable + Send + Sync; >>>> >>>> + /// The additional data carried by the [`MiscDeviceRegistration`] for this [`MiscDevice`]. >>>> + /// If no additional data is required than the unit type `()` should be used. >>>> + /// >>>> + /// This data can be accessed in [`MiscDevice::open()`] using >>>> + /// [`MiscDeviceRegistration::data()`]. >>>> + type RegistrationData: Sync; >>> >>> Why do we require `Sync` here? >> >> Needed for `MiscDeviceRegistration` to be `Send`, see response above. > > Even if `MiscDeviceRegistration` is non-Send, the registration data must > still be Sync. The f_ops->open callback can *always* be called from any > thread no matter what we do here, so the data it gives you access must > always be Sync no matter what. Right I meant to write `Sync` sorry. Cheers Christian