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([2001:871:22a:3372::1ad1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a53229de7csm4943387f8f.14.2025.06.07.08.39.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Jun 2025 08:39:32 -0700 (PDT) Message-ID: <68fd9ef6-a93a-413a-99b4-1b4d100aecb9@gmail.com> Date: Sat, 7 Jun 2025 17:39:31 +0200 Precedence: bulk X-Mailing-List: rust-for-linux@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: Benno Lossin , Miguel Ojeda , Danilo Krummrich , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Arnd Bergmann , Greg Kroah-Hartman , Lee Jones , Daniel Almeida Cc: =?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> <3c1c0563-7f48-4222-a28d-316f885bcad4@gmail.com> <89066f83-db7f-405c-b3b5-ce553f8e6b48@gmail.com> <8f491c61-e7b2-4a1f-b4f8-8ff691015655@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 07.06.25 5:37 PM, Benno Lossin wrote: > On Sat Jun 7, 2025 at 1:34 PM CEST, Christian Schrefl wrote: >> Yeah I understand that its not UB, but to me it seems a bit fragile and opaque why it is allowed. >> That's what I meant by "a bit iffy". > > What's fragile about it? That someone could add a non-opaque field to > the struct? Or that one is not allowed to take an `&`? Yeah that a added field could cause UB seems bad to me. > >> Alright but I doubt that realistic, since the `Data` would always at >> least be shared between the owner of `MiscDeviceRegistration` and the >> `fops` implementation. Meaning its always shared with syscall context >> and I don't think it makes sense to have a registration owed in >> that context. > > That might be the case, but I think we should have this as a general > design guideline: avoid unnecessary trait bounds. Alright seems fine to me. Cheers Christian