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charset=UTF-8 Date: Sun, 15 Jun 2025 21:59:39 +0900 Message-Id: From: "Alexandre Courbot" To: "Boqun Feng" Cc: "Daniel Almeida" , "Miguel Ojeda" , "Alex Gaynor" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , "Danilo Krummrich" , , Subject: Re: [PATCH v6] rust: kernel: add support for bits/genmask macros X-Mailer: aerc 0.20.1-0-g2ecb8770224a References: <20250610-topic-panthor-rs-genmask-v6-1-50fa1a981bc1@collabora.com> In-Reply-To: X-ClientProxiedBy: TYAPR01CA0079.jpnprd01.prod.outlook.com (2603:1096:404:2c::19) To CH2PR12MB3990.namprd12.prod.outlook.com (2603:10b6:610:28::18) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PR12MB3990:EE_|SA3PR12MB8809:EE_ X-MS-Office365-Filtering-Correlation-Id: fde870dd-2026-4855-b1a4-08ddac0c7e89 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|10070799003; 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>> > + } >>=20 >> From this check I assumed that you interpret `range` as non-inclusive, >> since `range.end =3D=3D 32` is valid on u32... >>=20 >> > + let high =3D $checked_bit(range.end)?; >>=20 >> ... however IIUC `checked_bit` will return `None` here in such a case. >> Should the argument be `range.end - 1`? >>=20 >> Your examples do seem to interpret the range as inclusive though, so >> probably the check should be `|| range.end >=3D <$ty>::BITS`. But that >> triggers the question, is it ok to use `Range` that way, when its >> documentation specifically states that it is bounded exclusively above? >> We could use `RangeInclusive` to match the semantics, which would >> require us to write the ranges as `0..=3D7`. At least it is clear that t= he >> upper bound is inclusive. >>=20 >> ... or we make the methods generic against `RangeBounds` and allow both >> `Range` and `RangeInclusive` to be used. But I'm concerned that callers >> might use `0..1` thinking it is inclusive while it is not. >>=20 > > I think generic over `RangeBounds` is a good idea, and we should > .is_emtpy() or .contains() instead of comparison + boolean operation > when possible. Seems we need a function to check whether one range > contains another range, which is not available currently? > > I would not be worried about callers treating `0..1` as inclusive: this > is a Rust project anyway, we need to learn the correct semantics of > expressions eventually ;-) Right, your comment made me realize that my concern could apply to all uses of the ranges, including the basic and common slice access. So following the expected semantics and offering the caller the option to use an inclusive or non-inclusive range through `RangeBounds` indeed sounds like the way to go.