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Tue, 9 Dec 2025 06:23:03 -0800 Date: Tue, 9 Dec 2025 16:22:58 +0200 From: Zhi Wang To: Dirk Behme CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFC 1/7] rust: pci: expose sriov_get_totalvfs() helper Message-ID: <20251209162258.541a2a5b@inno-ThinkPad-X280> In-Reply-To: References: <20251206124208.305963-1-zhiw@nvidia.com> <20251206124208.305963-2-zhiw@nvidia.com> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF0001A0FA:EE_|LV5PR12MB9754:EE_ X-MS-Office365-Filtering-Correlation-Id: b9873472-81f4-4270-f8c3-08de372e838b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|36860700013|82310400026|7053199007|13003099007; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Dec 2025 14:23:24.6441 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b9873472-81f4-4270-f8c3-08de372e838b X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0001A0FA.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV5PR12MB9754 On Sun, 7 Dec 2025 08:12:10 +0100 Dirk Behme wrote: > On 06.12.25 13:42, Zhi Wang wrote: snip > In the thread [1] there was some discussion about the `if {} else {}` > "style". From that discussion I "distilled" 6 options [2] which I > liked for having an overview :) Of course not all of these applied > there (const), neither will they here. And all have pros and cons. I > think in the end option #4 was selected. > > What's about to do something similar here (and in the 2/7 patch as > well)? > > if vfs == 0 { > return Err(ENODEV); > } > > Ok(vfs) > > Dirk > Hey Dirk: Thanks for the detailed summary! As a C programmer before, I tend to do as above, because it improves a lot of readability on success path. While playing with rust, I tend to use 5). Personally, I try to stay away from if let chains, as some lifecycle changes happen in rust 2024 [1]. It wouldn't bite right now, but stay away from the bumps. :) As Miguel's comment in another thread, I would improve this as discussed. [1] https://doc.rust-lang.org/edition-guide/rust-2024/temporary-if-let-scope.html > [1] > https://lore.kernel.org/rust-for-linux/CANiq72kiscT5euAUjcSzvxMzM9Hdj8aQGeUN_pVF-vHf3DhBuQ@mail.gmail.com/ > > [2] Options distilled from the thread [1]: > > 1. > > if let Some(sum) = addr.checked_add(PAGE_SIZE - 1) { > return Some(sum & PAGE_MASK); > } > None > > > 2. > > addr.checked_add(PAGE_SIZE - 1).map(|sum| sum & PAGE_MASK) > > > 3. > > if let Some(sum) = addr.checked_add(PAGE_SIZE - 1) { > Some(sum & PAGE_MASK); > } else { > None > } > > > 4. > > let Some(sum) = addr.checked_add(PAGE_SIZE - 1) else { > return None; > }; > > Some(sum & PAGE_MASK) > > > 5. > > match addr.checked_add(PAGE_SIZE - 1) { > Some(v) => Some(v & PAGE_MASK), > None => None, > } > > 6. > > Some(addr.checked_add(PAGE_SIZE - 1)? & PAGE_MASK) >