Date:   Wed, 22 Feb 2023 19:55:37 +0000
From:   Gary Guo <gary@garyguo.net>
To:     Heghedus Razvan <heghedus.razvan@protonmail.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Asahi Lina <lina@asahilina.net>,
        Boqun Feng <boqun.feng@gmail.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        =?UTF-8?B?QmrDtnJu?= Roy Baron <bjorn3_gh@protonmail.com>,
        John Stultz <jstultz@google.com>,
        Stephen Boyd <sboyd@kernel.org>, linux-kernel@vger.kernel.org,
        rust-for-linux@vger.kernel.org, asahi@lists.linux.dev
Subject: Re: [PATCH] rust: time: New module for timekeeping functions
Message-ID: <20230222195537.3462c1c3.gary@garyguo.net>
In-Reply-To: <p7e4M5-kxxScH56bBMtlzht2_m33oSfMPHtExSVbDn0WIPYBEbiJjr2NvNhqCJotFhmYqH5h27EWPDhfSmmST0D-dSU1Alq4_BzDQUR48FA=@protonmail.com>
References: <20230221-gpu-up-time-v1-1-bf8fe74b7f55@asahilina.net>
        <87v8jvnqq4.ffs@tglx>
        <Y/TP6as7qqwfcI42@boqun-archlinux>
        <87h6vfnh0f.ffs@tglx>
        <7b93bf74-abdc-f8c1-9a12-7c7f080f9e19@asahilina.net>
        <87edqioo1e.ffs@tglx>
        <p7e4M5-kxxScH56bBMtlzht2_m33oSfMPHtExSVbDn0WIPYBEbiJjr2NvNhqCJotFhmYqH5h27EWPDhfSmmST0D-dSU1Alq4_BzDQUR48FA=@protonmail.com>
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?8NUTQIZqLC7ooFQ1poCYZeKhGZxOmVZuRL4O7ZOXqbuYNmfxamL3x9tF5Iec?=
 =?us-ascii?Q?rp4RfQgcC7uZQdF56WjbbZX6RmhQxEKL1/kcDNPTtF2W6upALeYvS4H5JtKg?=
 =?us-ascii?Q?O+wwLCmF20BGHX0TSF3vVpDyifp7GCIhPG3aeW7qqjUpjC6qkuIF7prYiaa/?=
 =?us-ascii?Q?bwgdODGOdzfDj4iaH7E9N2J0VYbTsn2zupdZccSkHcumebNEO7H/EbNE03R+?=
 =?us-ascii?Q?o4VkXzJvEqNAOAMC9ezwUKSR13vZV06at8/QW54CSLh/+rd83s8EaG3bvpLz?=
 =?us-ascii?Q?SUi7mPq8XYS0TdYXxRVhZGzJvbr/JeFfmUudJ9ifOOGCplgXBa2bST+gLv51?=
 =?us-ascii?Q?YuPHPRUNGZoARyS6v1uqqzoSxsplIQplRmG9cR6//Xvwn72YYdgZ2AJsIkII?=
 =?us-ascii?Q?7iQHblqCqy6hEEcbwxUzdiLPV87yHKC59hixuwQNhP3fLVYNBHC1qNcYmW8J?=
 =?us-ascii?Q?Zk0B9cFql5kECz5mTWqghUn3LusByth7Qiw8yPEzawNfnwpFkXejRY9QPiOS?=
 =?us-ascii?Q?DJU+VEsU6uaq6SwLWvYRntVCW/IapsMo33sXHT348fl3oCAM2k5ZVr6dS1d9?=
 =?us-ascii?Q?ynqACMFuRQE0dR1Wyus/3BskObbZ0p/dZl43sCLsQ6UeIkj+mnbSNAwSZ/g3?=
 =?us-ascii?Q?zVbBT9Z0BXdK9YhX4bFGn0ALVrGAytOUJyczq+vRb37U8JCP1Y8btUfJSjl6?=
 =?us-ascii?Q?NMEFHyXBeBdfb5OWofEQhzpJ47/HIAOfQAylgMhCsW7otBkE9G1j48uDNa4S?=
 =?us-ascii?Q?J0j3ISiS8rLIlNnO3eAr0/NDtgT0Pz9Cnxzgp8unprfdwe8HjVZxoJ25N5xc?=
 =?us-ascii?Q?iappDCvwneOMev8TzVVE20CfrLtd1Wf1mStT+ykU7fB86Ho4AuIFhvtP7xUq?=
 =?us-ascii?Q?x/sV62Q7/MFCo8cb9zdoORUvp+44sA3vGLv/YXy0p2RNYSI3OAID7LCAWijC?=
 =?us-ascii?Q?dAi7NrJvXohyBCwrDZM26ykpg1RP96TlX0pAfSnODFH3mvMsinankpEv7npv?=
 =?us-ascii?Q?ZJpDz2AxXNq92s82mwYpN0uZfj0jJ6VS9bylvsqW3BDInymuH+SS6emGBt0k?=
 =?us-ascii?Q?JXaTlYodFqR5bpjtzOYt6Hc5RTz/lKWu+aK07UruFYFoDX4piSFlbZNzcJGm?=
 =?us-ascii?Q?Jty03mIyoRW68qK+vUzOoGYAiOX0g5xuQv/tgX0aCMGlzCwikYEaj+ohd6Cd?=
 =?us-ascii?Q?r/htxlGgH4ZrE4DxzuatGDRpYBrwoB2uFepGRFafEwLxR4cpYjYtarvvpber?=
 =?us-ascii?Q?9uXi/QpEb/C7GpjBxf1f0GF2eRppMcQXEi9lAWnTdAaaWE+y9E1dkt+o67k/?=
 =?us-ascii?Q?0qIgOCeSBLmmHJTj8gWtPLaZDCrMonk24YX5fVPk7b5tuvfjFr+O/u9aTDAO?=
 =?us-ascii?Q?5HovYbkZpHYuevc7aCse+X7hpsaTBUlD6EVQzB73HWJ3SydCqsvdQRf+B7WZ?=
 =?us-ascii?Q?QlegyoPz0kZEoP85S/Exnyi33NrNjNH/FfYPeI690nOOlqNiWcc+vfIkk8Dl?=
 =?us-ascii?Q?CITCLgokQdZwug5sGx1I/yVSbnbygUnKsX6OaUIxGrnIBE3HfT/ortOzbCZC?=
 =?us-ascii?Q?yBRyxSqx5LkiMIZBRPVd5Nfia6xJMmQfho7GI+SV?=
X-OriginatorOrg: garyguo.net
X-MS-Exchange-CrossTenant-Network-Message-Id: 2f130720-5e06-40a4-dbea-08db150ec57b
X-MS-Exchange-CrossTenant-AuthSource: LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Feb 2023 19:55:39.1586
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Fotp99F1z/ekB8wiv0slYYBw40q5WK3J+Hu7pNMDKKmiPddfgG6nYVCl/PIhHLW+ML06zRhaGyqAa3RXNB0iNA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CWLP265MB1889
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 21 Feb 2023 21:33:42 +0000
Heghedus Razvan <heghedus.razvan@protonmail.com> wrote:

> On Tuesday, February 21st, 2023 at 8:45 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > That's the same the Rust std time semantics:
> > 
> > Duration = Instance - Instance valid
> > Duration = Systemtime - SystemTime valid
> > Duration = Systemtime - Instance invalid
> > 
> > No?
> >   
> I agree with Thomas on this one. The Rust type system is really powerful and we should take advantage of it. Time deltas can be enforced to be from the same clock at compile time.
> Just for the sake of it, I wrote a small example on how this can be achieve: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=1d0f70bb5329b181f203ce7270e2957a
> 

`NowTime` don't need the type parameter. Here's a slightly more polished
version (also with names changed a bit so it looks more "Rusty"):

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=83702f491050da1c67ab9aa129103f7d

Best,
Gary