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AJvYcCVP53oNYolh4pHnEWvSqdTzuM3vK29jGF25CiT80UHU754moitBKiTjJgGWLg9xj7/d/KbXRGpi2kC2hMU=@vger.kernel.org X-Gm-Message-State: AOJu0Yyz4zEDGFLsy9DJBFNDwcz2e2lWwkC4RTkdwcD7bQ/elh1Snic8 OhPVJwHJs7w/EHwLGsKWHzCqRoRHnuqHVvbAHVoOWMRovYK9VNvGRs+HbaVpoEuawY1Ygn6Afdn Mj1MZtAG9hf8mNg== X-Google-Smtp-Source: AGHT+IHugWNIf0NTcJ1BqVmz9bIucegvlBQBCECxMHN4Jb5Pzy5PsgyGHPknwC9dbNhN2W5DuUZR8ZPXN7RoR94= X-Received: from wmbbe3.prod.google.com ([2002:a05:600c:1e83:b0:43b:c914:a2d9]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3d97:b0:43c:efed:732d with SMTP id 5b1f17b1804b1-43d437c32bcmr62405395e9.16.1742459665813; Thu, 20 Mar 2025 01:34:25 -0700 (PDT) Date: Thu, 20 Mar 2025 08:34:21 +0000 In-Reply-To: <20250319203112.131959-2-dakr@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250319203112.131959-1-dakr@kernel.org> <20250319203112.131959-2-dakr@kernel.org> Message-ID: Subject: Re: [PATCH 1/4] rust: device: implement Device::parent() From: Alice Ryhl To: Danilo Krummrich Cc: bhelgaas@google.com, gregkh@linuxfoundation.org, rafael@kernel.org, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@kernel.org, tmgross@umich.edu, linux-pci@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On Wed, Mar 19, 2025 at 09:30:25PM +0100, Danilo Krummrich wrote: > Device::parent() returns a reference to the device' parent device, if > any. > > Signed-off-by: Danilo Krummrich > --- > rust/kernel/device.rs | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs > index 21b343a1dc4d..76b341441f3f 100644 > --- a/rust/kernel/device.rs > +++ b/rust/kernel/device.rs > @@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device { > self.0.get() > } > > + /// Returns a reference to the parent device, if any. > + pub fn parent<'a>(&self) -> Option<&'a Self> { > + // SAFETY: By the type invariant `self.as_raw()` is always valid. > + let parent = unsafe { *self.as_raw() }.parent; This means: 1. Copy the entire `struct device` onto the stack. 2. Read the `parent` field of the copy. Please write this instead to only read the `parent` field: let parent = unsafe { *self.as_raw().parent }; > + if parent.is_null() { > + None > + } else { > + // SAFETY: Since `parent` is not NULL, it must be a valid pointer to a `struct device`. > + Some(unsafe { Self::as_ref(parent) }) > + } > + } > + > /// Convert a raw C `struct device` pointer to a `&'a Device`. > /// > /// # Safety > -- > 2.48.1 >