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charset=UTF-8 Date: Tue, 21 Apr 2026 10:22:34 +0900 Message-Id: Cc: "gary@garyguo.net" , "Joel Fernandes" , "dakr@kernel.org" , "Eliot Courtney" , "John Hubbard" , "rust-for-linux@vger.kernel.org" Subject: Re: [PATCH v5 4/6] gpu: nova-core: add FbHal::frts_size() for GA100 support From: "Alexandre Courbot" To: "Timur Tabi" References: <20260417191359.1307434-1-ttabi@nvidia.com> <20260417191359.1307434-5-ttabi@nvidia.com> In-Reply-To: X-ClientProxiedBy: OS0P286CA0048.JPNP286.PROD.OUTLOOK.COM (2603:1096:604:9e::17) 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: MN2PR12MB3997:EE_|MN0PR12MB6317:EE_ X-MS-Office365-Filtering-Correlation-Id: 6720212d-fa4b-4255-17cc-08de9f447c86 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|10070799003|1800799024|366016|18096099003|22082099003|18002099003|56012099003; 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It refers to this FbHal function: > > /// Returns `true` is display is supported. > fn supports_display(&self, bar: &Bar0) -> bool; > > It reads an arch-specific register to determine whether display is "suppo= rted". There is no > register that tells us "needs FRTS", and so that's why frts_size() exists= . > >> > So I guess what I'm really trying to say is that I've done a lot of re= search into how this code >> > works, and it's written the way I wrote it for a reason. >> >=20 >> > As for using a Trait to define a default value that is just overridden= by GA100, that would be >> > okay, >> > but it wouldn't be any clearer or more accurate. >> >=20 >> > I personally don't like `super::tu102::frts_size_tu102()` and I think = both tu102::frts_size() >> > and >> > ga102::frts_size() should just return u64::SZ_1M, but I don't care eno= ugh to make a stink about >> > it. >>=20 >> Thanks, that's a very good explanation how the reason the code is writte= n as is. >> With the information above, I'm happy with current approach. >>=20 >> Acked-by: Gary Guo > > Thanks. > >> I think it's important to note that not all of us have knowledge (or eve= n >> access) to some of the context that you have, so something that may seem= obvious >> to you could require some additional background or reasons to be added i= n commit >> message or comment. > > Unfortunately, the process to boot GSP-RM is so convoluted that it's not = really possible to document > everything publicly. A lot of it just porting OpenRM (and to some degree= Nouveau) to Rust and > saying "Well, this is how it is". In fact, it's much easier to mimic Ope= nRM than it is to actually > read the internal documentation to figure out what to do. > >> Also, in the commit message you mentioned >>=20 >> > Introduce FbHal method frts_size() to return the size of the FRTS >> > window.=C2=A0 GA100 is a special case in that there is no FRTS, and so >> > the size must be set to 0. >>=20 >> and this probably should be corrected. > > Ugh, I thought I caught all of these. > > Alex, if you wouldn't mind, change that last sentence to: > > "GA100 is a special case in that although there is an FRTS, its size must= arbitrarily be set to 0." Sure, I've fixed it on my staging branch. With this last point cleared, you can consider this series merged as I will push it as soon as drm-rust-next reopens. It also makes the Blackwell series a bit smoother, so I'm happy we can push it first! > > > If you update to the latest git, you can use the new "git history" comman= d: > https://github.blog/open-source/git/highlights-from-git-2-54/ Thanks for the pointer, I do commit log edits *a lot* and this is definitely going to help!