linux-kernel - Re: [PATCH] rust: enable `clippy::ptr_as

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Message-ID: <CAJ-ks9mkbs9KG5D5yETvOJfeqyzTts1gVZyNAogbxjXbwOreZg@mail.gmail.com>
Date: Tue, 11 Mar 2025 16:44:11 -0400
From: Tamir Duberstein <tamird@...il.com>
To: kernel test robot <lkp@...el.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas@...sle.eu>, 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>, Brendan Higgins <brendan.higgins@...ux.dev>, 
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, 
	Bjorn Helgaas <helgaas@...nel.org>, oe-kbuild-all@...ts.linux.dev, 
	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
Subject: Re: [PATCH] rust: enable `clippy::ptr_as_ptr` lint

On Tue, Mar 11, 2025 at 3:22 PM kernel test robot <lkp@...el.com> wrote:
>
> Hi Tamir,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on ff64846bee0e7e3e7bc9363ebad3bab42dd27e24]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Tamir-Duberstein/rust-enable-clippy-ptr_as_ptr-lint/20250308-004557
> base:   ff64846bee0e7e3e7bc9363ebad3bab42dd27e24
> patch link:    https://lore.kernel.org/r/20250307-ptr-as-ptr-v1-1-582d06514c98%40gmail.com
> patch subject: [PATCH] rust: enable `clippy::ptr_as_ptr` lint
> config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20250312/202503120332.YTCpFEvv-lkp@intel.com/config)
> compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250312/202503120332.YTCpFEvv-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202503120332.YTCpFEvv-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> >> warning: `as` casting between raw pointers without changing its mutability
>    --> rust/kernel/firmware.rs:64:35
>    |
>    64 |         let ret = unsafe { func.0(pfw as _, name.as_char_ptr(), dev.as_raw()) };
>    |                                   ^^^^^^^^ help: try `pointer::cast`, a safer alternative: `pfw.cast()`
>    |
>    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_as_ptr
>    = note: requested on the command line with `-W clippy::ptr-as-ptr`
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Indeed missed this one because I wasn't building with
CONFIG_RUST_FW_LOADER_ABSTRACTIONS. Fixed in v3 by:

diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index c5162fdc95ff..74df815d2f4e 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -58,10 +58,11 @@ impl Firmware {
     fn request_internal(name: &CStr, dev: &Device, func: FwFunc) ->
Result<Self> {
         let mut fw: *mut bindings::firmware = core::ptr::null_mut();
         let pfw: *mut *mut bindings::firmware = &mut fw;
+        let pfw: *mut *const bindings::firmware = pfw.cast();

         // SAFETY: `pfw` is a valid pointer to a NULL initialized
`bindings::firmware` pointer.
         // `name` and `dev` are valid as by their type invariants.
-        let ret = unsafe { func.0(pfw as _, name.as_char_ptr(),
dev.as_raw()) };
+        let ret = unsafe { func.0(pfw, name.as_char_ptr(), dev.as_raw()) };
         if ret != 0 {
             return Err(Error::from_errno(ret));
         }

By the way, it would be great if the email also included the rustc version used.