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charset=UTF-8 Date: Tue, 04 Nov 2025 23:15:03 +0900 Message-Id: Cc: "Miguel Ojeda" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Trevor Gross" , "Danilo Krummrich" , "Nathan Chancellor" , "Nicolas Schier" , , , Subject: Re: [PATCH v2] rust: enable slice_flatten feature and provide it through an extension trait From: "Alexandre Courbot" To: "Alice Ryhl" , "Alexandre Courbot" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20251104-b4-as-flattened-v2-1-b042d8715a8d@nvidia.com> In-Reply-To: X-ClientProxiedBy: TYCP301CA0085.JPNP301.PROD.OUTLOOK.COM (2603:1096:405:7b::7) To CH2PR12MB3990.namprd12.prod.outlook.com (2603:10b6:610:28::18) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PR12MB3990:EE_|BY5PR12MB4243:EE_ X-MS-Office365-Filtering-Correlation-Id: ffa72466-e7be-45a6-f27a-08de1bac8e35 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|10070799003|376014|7416014|366016|1800799024|13003099007|7053199007; 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>>=20 >> This extension trait can be removed once the MSRV passes 1.80. >>=20 >> Suggested-by: Miguel Ojeda >> Link: https://lore.kernel.org/all/CANiq72kK4pG=3DO35NwxPNoTO17oRcg1yfGcv= r3=3D=3DFi4edr+sfmw@mail.gmail.com/ >> Acked-by: Danilo Krummrich >> Acked-by: Miguel Ojeda >> Signed-off-by: Alexandre Courbot >> --- >> This patch was part of the Nova GSP boot series [1], but since it >> requires attention from the core Rust team (and possibly the build >> maintainers?) and is otherwise buried under Nova patches, I am taking >> the freedom to send it separately for visibility. >>=20 >> For v2, the methods are aligned with the final names of the standard >> library, and the extension trait is only visible when needed. This >> simplifies both the patch, and the extra labor for user code. >>=20 >> [1] https://lore.kernel.org/all/20251029-gsp_boot-v7-0-34227afad347@nvid= ia.com/ >> [2] https://lore.kernel.org/all/CANiq72kK4pG=3DO35NwxPNoTO17oRcg1yfGcvr3= =3D=3DFi4edr+sfmw@mail.gmail.com/ > > With the below concern verified, you may add: > Reviewed-by: Alice Ryhl Thanks! You may want to check the v3 that I just posted [1] which also addressed your comment about having the extensions trait in the prelude. [1] https://lore.kernel.org/rust-for-linux/20251104-b4-as-flattened-v3-1-6c= b9c26b45cd@nvidia.com/T/#u > >> diff --git a/scripts/Makefile.build b/scripts/Makefile.build >> index d0ee33a487be..a84b9e3171a3 100644 >> --- a/scripts/Makefile.build >> +++ b/scripts/Makefile.build >> @@ -308,6 +308,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE >> =20 >> # The features in this list are the ones allowed for non-`rust/` code. >> # >> +# - Stable since Rust 1.80.0: `feature(slice_flatten)`. >> # - Stable since Rust 1.81.0: `feature(lint_reasons)`. >> # - Stable since Rust 1.82.0: `feature(asm_const)`, >> # `feature(offset_of_nested)`, `feature(raw_ref_op)`. >> @@ -317,7 +318,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE >> # >> # Please see https://github.com/Rust-for-Linux/linux/issues/2 for detai= ls on >> # the unstable features in use. >> -rust_allowed_features :=3D asm_const,asm_goto,arbitrary_self_types,lint= _reasons,offset_of_nested,raw_ref_op,used_with_arg >> +rust_allowed_features :=3D asm_const,asm_goto,arbitrary_self_types,lint= _reasons,offset_of_nested,raw_ref_op,slice_flatten,used_with_arg > > You should double-check, but I don't think you need to list it here > because all uses of the unstable method are under the `rust/` directory. I will check that, and indeed the comment above says as much.