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Message-ID: <68014084.0c0a0220.394e75.122c@mx.google.com>
Date: Thu, 17 Apr 2025 10:55:13 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
Nathan Chancellor <nathan@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...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>,
Brendan Higgins <brendan.higgins@...ux.dev>,
David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Luis Chamberlain <mcgrof@...nel.org>,
Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>,
Saravana Kannan <saravanak@...gle.com>,
Abdiel Janulgue <abdiel.janulgue@...il.com>,
Daniel Almeida <daniel.almeida@...labora.com>,
Robin Murphy <robin.murphy@....com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
FUJITA Tomonori <fujita.tomonori@...il.com>,
Nicolas Schier <nicolas.schier@...ux.dev>,
Frederic Weisbecker <frederic@...nel.org>, Lyude Paul <lyude@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
rust-for-linux@...r.kernel.org, linux-kselftest@...r.kernel.org,
kunit-dev@...glegroups.com, linux-pci@...r.kernel.org,
linux-block@...r.kernel.org, devicetree@...r.kernel.org,
dri-devel@...ts.freedesktop.org, netdev@...r.kernel.org
Subject: Re: [PATCH v9 4/6] rust: enable `clippy::as_underscore` lint
On Wed, Apr 16, 2025 at 01:36:08PM -0400, Tamir Duberstein wrote:
> In Rust 1.63.0, Clippy introduced the `as_underscore` lint [1]:
>
> > The conversion might include lossy conversion or a dangerous cast that
> > might go undetected due to the type being inferred.
> >
> > The lint is allowed by default as using `_` is less wordy than always
> > specifying the type.
>
> Always specifying the type is especially helpful in function call
> contexts where the inferred type may change at a distance. Specifying
> the type also allows Clippy to spot more cases of `useless_conversion`.
>
> The primary downside is the need to specify the type in trivial getters.
> There are 4 such functions: 3 have become slightly less ergonomic, 1 was
> revealed to be a `useless_conversion`.
>
> While this doesn't eliminate unchecked `as` conversions, it makes such
> conversions easier to scrutinize. It also has the slight benefit of
> removing a degree of freedom on which to bikeshed. Thus apply the
> changes and enable the lint -- no functional change intended.
>
> Link: https://rust-lang.github.io/rust-clippy/master/index.html#as_underscore [1]
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Signed-off-by: Tamir Duberstein <tamird@...il.com>
> ---
> Makefile | 1 +
> rust/kernel/block/mq/operations.rs | 2 +-
> rust/kernel/block/mq/request.rs | 2 +-
> rust/kernel/device_id.rs | 2 +-
> rust/kernel/devres.rs | 15 ++++++++-------
> rust/kernel/dma.rs | 2 +-
> rust/kernel/error.rs | 2 +-
> rust/kernel/io.rs | 18 +++++++++---------
> rust/kernel/miscdevice.rs | 2 +-
> rust/kernel/of.rs | 6 +++---
> rust/kernel/pci.rs | 9 ++++++---
> rust/kernel/str.rs | 8 ++++----
> rust/kernel/workqueue.rs | 2 +-
> 13 files changed, 38 insertions(+), 33 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 04a5246171f9..57080a64913f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -475,6 +475,7 @@ export rust_common_flags := --edition=2021 \
> -Wunreachable_pub \
> -Wclippy::all \
> -Wclippy::as_ptr_cast_mut \
> + -Wclippy::as_underscore \
> -Wclippy::ignored_unit_patterns \
> -Wclippy::mut_mut \
> -Wclippy::needless_bitwise_bool \
> diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
> index 864ff379dc91..d18ef55490da 100644
> --- a/rust/kernel/block/mq/operations.rs
> +++ b/rust/kernel/block/mq/operations.rs
> @@ -101,7 +101,7 @@ impl<T: Operations> OperationsVTable<T> {
> if let Err(e) = ret {
> e.to_blk_status()
> } else {
> - bindings::BLK_STS_OK as _
> + bindings::BLK_STS_OK as u8
> }
> }
>
> diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
> index af5c9ac94f36..22697104bf8c 100644
> --- a/rust/kernel/block/mq/request.rs
> +++ b/rust/kernel/block/mq/request.rs
> @@ -125,7 +125,7 @@ pub fn end_ok(this: ARef<Self>) -> Result<(), ARef<Self>> {
> // success of the call to `try_set_end` guarantees that there are no
> // `ARef`s pointing to this request. Therefore it is safe to hand it
> // back to the block layer.
> - unsafe { bindings::blk_mq_end_request(request_ptr, bindings::BLK_STS_OK as _) };
> + unsafe { bindings::blk_mq_end_request(request_ptr, bindings::BLK_STS_OK as u8) };
>
We could consider defining a const block::mq::BLK_STATUS_OK as:
const BLK_STATUS_OK: u8 = bindings::BLK_STS_OK as u8;
, because repeating the as pattern is a bit err-prone. But maybe in a
later patch.
> Ok(())
> }
> diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
> index e5859217a579..4063f09d76d9 100644
> --- a/rust/kernel/device_id.rs
> +++ b/rust/kernel/device_id.rs
> @@ -82,7 +82,7 @@ impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {
> unsafe {
> raw_ids[i]
> .as_mut_ptr()
> - .byte_offset(T::DRIVER_DATA_OFFSET as _)
> + .byte_add(T::DRIVER_DATA_OFFSET)
> .cast::<usize>()
> .write(i);
> }
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index f7e8f5f53622..70d12014e476 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -45,7 +45,7 @@ struct DevresInner<T> {
> /// # Example
> ///
> /// ```no_run
> -/// # use kernel::{bindings, c_str, device::Device, devres::Devres, io::{Io, IoRaw}};
> +/// # use kernel::{bindings, c_str, device::Device, devres::Devres, ffi::c_void, io::{Io, IoRaw}};
> /// # use core::ops::Deref;
> ///
> /// // See also [`pci::Bar`] for a real example.
> @@ -59,19 +59,19 @@ struct DevresInner<T> {
> /// unsafe fn new(paddr: usize) -> Result<Self>{
> /// // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is
> /// // valid for `ioremap`.
> -/// let addr = unsafe { bindings::ioremap(paddr as _, SIZE as _) };
> +/// let addr = unsafe { bindings::ioremap(paddr as bindings::phys_addr_t, SIZE) };
/// let addr = unsafe { bindings::ioremap(bindings::phys_addr_t::from(paddr), SIZE) };
better? Or even with .into()
/// let addr = unsafe { bindings::ioremap(paddr.into(), SIZE) };
> /// if addr.is_null() {
> /// return Err(ENOMEM);
> /// }
> ///
> -/// Ok(IoMem(IoRaw::new(addr as _, SIZE)?))
> +/// Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
> /// }
> /// }
> ///
> /// impl<const SIZE: usize> Drop for IoMem<SIZE> {
> /// fn drop(&mut self) {
> /// // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.
> -/// unsafe { bindings::iounmap(self.0.addr() as _); };
> +/// unsafe { bindings::iounmap(self.0.addr() as *mut c_void); };
> /// }
> /// }
> ///
[...]
> diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
> index 43ecf3c2e860..851a6339aa90 100644
> --- a/rust/kernel/dma.rs
> +++ b/rust/kernel/dma.rs
> @@ -38,7 +38,7 @@
> impl Attrs {
> /// Get the raw representation of this attribute.
> pub(crate) fn as_raw(self) -> crate::ffi::c_ulong {
> - self.0 as _
> + self.0 as crate::ffi::c_ulong
crate::ffi::c_ulong::from(self.0)
maybe, a C unsigned long should always be able to hold the whole `Attr`
and a lossly casting is what this function does.
> }
>
> /// Check whether `flags` is contained in `self`.
[...]
> @@ -70,19 +70,19 @@ pub fn maxsize(&self) -> usize {
> /// unsafe fn new(paddr: usize) -> Result<Self>{
> /// // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is
> /// // valid for `ioremap`.
> -/// let addr = unsafe { bindings::ioremap(paddr as _, SIZE as _) };
> +/// let addr = unsafe { bindings::ioremap(paddr as bindings::phys_addr_t, SIZE) };
Similarly:
/// let addr = unsafe { bindings::ioremap(paddr.into(), SIZE) };
or `from()`.
> /// if addr.is_null() {
> /// return Err(ENOMEM);
> /// }
> ///
> -/// Ok(IoMem(IoRaw::new(addr as _, SIZE)?))
> +/// Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
> /// }
> /// }
> ///
> /// impl<const SIZE: usize> Drop for IoMem<SIZE> {
> /// fn drop(&mut self) {
> /// // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.
> -/// unsafe { bindings::iounmap(self.0.addr() as _); };
> +/// unsafe { bindings::iounmap(self.0.addr() as *mut c_void); };
> /// }
> /// }
> ///
[...]
The rest looks good to me. Thanks!
Regards,
Boqun
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