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From: Danilo Krummrich <dakr@kernel.org>
To: Tamir Duberstein <tamird@gmail.com>
Cc: "Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	"FUJITA Tomonori" <fujita.tomonori@gmail.com>,
	"Rob Herring (Arm)" <robh@kernel.org>,
	"Maíra Canal" <mcanal@igalia.com>,
	"Asahi Lina" <lina@asahilina.net>,
	rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v16 1/4] rust: remove redundant `as _` casts
Date: Mon, 17 Feb 2025 12:06:29 +0100	[thread overview]
Message-ID: <Z7MYNQgo28sr_4RS@cassiopeiae> (raw)
In-Reply-To: <20250207-rust-xarray-bindings-v16-1-256b0cf936bd@gmail.com>

On Fri, Feb 07, 2025 at 08:58:24AM -0500, Tamir Duberstein wrote:
> Remove redundant casts added in commit 1bd8b6b2c5d3 ("rust: pci: add
> basic PCI device / driver abstractions") and commit 683a63befc73 ("rust:
> platform: add basic platform device / driver abstractions")

I thought of doing it the other way around: Do only the *required* changes in
commit "rust: types: add `ForeignOwnable::PointedTo`", i.e. no need to touch
this code at all. And then switch to cast() in a subsequent patch.

This way you don't need to remove (previously unnecessary) casts and then add
them back in.

> 
> While I'm churning this line, move the `.into_foreign()` call to its own
> statement to avoid churn in the next commit which adds a `.cast()` call.
> 
> Fixes: 1bd8b6b2c5d3 ("rust: pci: add basic PCI device / driver abstractions")
> Fixes: 683a63befc73 ("rust: platform: add basic platform device / driver abstractions")

No, at the time those casts were indeed necessary, because the types differed in
mutability.

"A Fixes: tag indicates that the patch fixes an issue in a previous commit." [1]

Even if the cast was unnecessary in the first place, it is at least questionable
to me whether this falls under "fixing an issue".

[1] https://docs.kernel.org/process/submitting-patches.html#reviewer-s-statement-of-oversight

> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> ---
>  rust/kernel/pci.rs      | 3 ++-
>  rust/kernel/platform.rs | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 4c98b5b9aa1e..6c3bc14b42ad 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -72,10 +72,11 @@ extern "C" fn probe_callback(
>  
>          match T::probe(&mut pdev, info) {
>              Ok(data) => {
> +                let data = data.into_foreign();
>                  // Let the `struct pci_dev` own a reference of the driver's private data.
>                  // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
>                  // `struct pci_dev`.
> -                unsafe { bindings::pci_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
> +                unsafe { bindings::pci_set_drvdata(pdev.as_raw(), data) };

Please do not factor this out, it is unnecessary for what you want to accomplish
with your commit.

>              }
>              Err(err) => return Error::to_errno(err),
>          }
> diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
> index 50e6b0421813..dea104563fa9 100644
> --- a/rust/kernel/platform.rs
> +++ b/rust/kernel/platform.rs
> @@ -63,10 +63,11 @@ extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ff
>          let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
>          match T::probe(&mut pdev, info) {
>              Ok(data) => {
> +                let data = data.into_foreign();
>                  // Let the `struct platform_device` own a reference of the driver's private data.
>                  // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
>                  // `struct platform_device`.
> -                unsafe { bindings::platform_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
> +                unsafe { bindings::platform_set_drvdata(pdev.as_raw(), data) };
>              }
>              Err(err) => return Error::to_errno(err),
>          }
> 
> -- 
> 2.48.1
> 

  reply	other threads:[~2025-02-17 11:06 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-07 13:58 [PATCH v16 0/4] rust: xarray: Add a minimal abstraction for XArray Tamir Duberstein
2025-02-07 13:58 ` [PATCH v16 1/4] rust: remove redundant `as _` casts Tamir Duberstein
2025-02-17 11:06   ` Danilo Krummrich [this message]
2025-02-07 13:58 ` [PATCH v16 2/4] rust: types: add `ForeignOwnable::PointedTo` Tamir Duberstein
2025-02-17  1:39   ` Benno Lossin
2025-02-17  1:58     ` Tamir Duberstein
2025-02-17 12:12   ` Danilo Krummrich
2025-02-17 14:02     ` Tamir Duberstein
2025-02-17 14:15       ` Danilo Krummrich
2025-02-17 14:21         ` Tamir Duberstein
2025-02-17 14:37           ` Danilo Krummrich
2025-02-17 14:47             ` Tamir Duberstein
2025-02-17 14:51               ` Danilo Krummrich
2025-02-17 15:50                 ` Tamir Duberstein
2025-02-17 16:35                   ` Danilo Krummrich
2025-02-17 17:03                     ` Miguel Ojeda
2025-02-17 17:03                   ` Miguel Ojeda
2025-02-17 17:03           ` Miguel Ojeda
2025-02-17 17:11             ` Tamir Duberstein
2025-02-17 17:24               ` Miguel Ojeda
2025-02-17 17:36                 ` Miguel Ojeda
2025-02-17 17:43                   ` Tamir Duberstein
2025-02-17 18:12                     ` Miguel Ojeda
2025-02-17 18:24                       ` Tamir Duberstein
2025-02-18  8:59     ` Andreas Hindborg
2025-02-07 13:58 ` [PATCH v16 3/4] rust: xarray: Add an abstraction for XArray Tamir Duberstein
2025-02-17 11:35   ` Danilo Krummrich
2025-02-17 13:43     ` Tamir Duberstein
2025-02-17 13:57       ` Danilo Krummrich
2025-02-07 13:58 ` [PATCH v16 4/4] MAINTAINERS: add entry for Rust XArray API Tamir Duberstein

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