linux-kernel - Re: [PATCH v4 3/9] rust: device: Move property

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Message-ID: <20250512172957.GB3463681-robh@kernel.org>
Date: Mon, 12 May 2025 12:29:57 -0500
From: Rob Herring <robh@...nel.org>
To: Remo Senekowitsch <remo@...nzli.dev>,
	Viresh Kumar <viresh.kumar@...aro.org>
Cc: Saravana Kannan <saravanak@...gle.com>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Dirk Behme <dirk.behme@...bosch.com>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v4 3/9] rust: device: Move property_present() to FwNode

On Sun, May 04, 2025 at 07:31:48PM +0200, Remo Senekowitsch wrote:
> The new FwNode abstraction will be used for accessing all device
> properties, so it must have the property_present method.
> 
> It's possible to duplicate the methods on the device itself, but since
> some of the methods on Device would have different type sigatures as the
> ones on FwNode, this would only lead to inconsistency and confusion.
> Hence, remove the method from Device.
> 
> There aren't any users to update yet.

But there is one going into 6.16 most likely with the cpufreq stuff[1] 
which complicates merging.

Rob

[1] https://lore.kernel.org/all/f7e96b7da77ac217be5ccb09b9309da28fd96c90.1745218976.git.viresh.kumar@linaro.org/

> 
> Signed-off-by: Remo Senekowitsch <remo@...nzli.dev>
> ---
>  rust/kernel/device/mod.rs      | 7 -------
>  rust/kernel/device/property.rs | 8 +++++++-
>  2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/rust/kernel/device/mod.rs b/rust/kernel/device/mod.rs
> index b4b7056eb80f8..15d89cd45e871 100644
> --- a/rust/kernel/device/mod.rs
> +++ b/rust/kernel/device/mod.rs
> @@ -6,7 +6,6 @@
>  
>  use crate::{
>      bindings,
> -    str::CStr,
>      types::{ARef, Opaque},
>  };
>  use core::{fmt, marker::PhantomData, ptr};
> @@ -200,12 +199,6 @@ pub fn fwnode(&self) -> Option<&property::FwNode> {
>          // defined as a `#[repr(transparent)]` wrapper around `fwnode_handle`.
>          Some(unsafe { &*fwnode_handle.cast() })
>      }
> -
> -    /// Checks if property is present or not.
> -    pub fn property_present(&self, name: &CStr) -> bool {
> -        // SAFETY: By the invariant of `CStr`, `name` is null-terminated.
> -        unsafe { bindings::device_property_present(self.as_raw().cast_const(), name.as_char_ptr()) }
> -    }
>  }
>  
>  // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
> diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
> index e75d55f5856cf..70593343bd811 100644
> --- a/rust/kernel/device/property.rs
> +++ b/rust/kernel/device/property.rs
> @@ -6,7 +6,7 @@
>  
>  use core::ptr;
>  
> -use crate::{bindings, types::Opaque};
> +use crate::{bindings, str::CStr, types::Opaque};
>  
>  /// A reference-counted fwnode_handle.
>  ///
> @@ -31,6 +31,12 @@ impl FwNode {
>      pub(crate) fn as_raw(&self) -> *mut bindings::fwnode_handle {
>          self.0.get()
>      }
> +
> +    /// Checks if property is present or not.
> +    pub fn property_present(&self, name: &CStr) -> bool {
> +        // SAFETY: By the invariant of `CStr`, `name` is null-terminated.
> +        unsafe { bindings::fwnode_property_present(self.as_raw().cast_const(), name.as_char_ptr()) }
> +    }
>  }
>  
>  // SAFETY: Instances of `FwNode` are always reference-counted.
> -- 
> 2.49.0
>