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Date: Fri, 17 Oct 2025 13:01:46 +0200
Message-Id: <DDKJO7HME02Z.2HXY61JBM3GZN@kernel.org>
Cc: <rust-for-linux@vger.kernel.org>, <bhelgaas@google.com>,
 <kwilczynski@kernel.org>, <ojeda@kernel.org>, <alex.gaynor@gmail.com>,
 <boqun.feng@gmail.com>, <gary@garyguo.net>, <bjorn3_gh@protonmail.com>,
 <lossin@kernel.org>, <a.hindborg@kernel.org>, <aliceryhl@google.com>,
 <tmgross@umich.edu>, <linux-pci@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <cjia@nvidia.com>, <smitra@nvidia.com>,
 <ankita@nvidia.com>, <aniketa@nvidia.com>, <kwankhede@nvidia.com>,
 <targupta@nvidia.com>, <zhiwang@kernel.org>, <acourbot@nvidia.com>,
 <joelagnelf@nvidia.com>, <jhubbard@nvidia.com>, <markus.probst@posteo.de>
To: "Zhi Wang" <zhiw@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v2 2/5] rust: io: factor out MMIO read/write macros
References: <20251016210250.15932-1-zhiw@nvidia.com>
 <20251016210250.15932-3-zhiw@nvidia.com>
In-Reply-To: <20251016210250.15932-3-zhiw@nvidia.com>

On Thu Oct 16, 2025 at 11:02 PM CEST, Zhi Wang wrote:
> @@ -122,10 +139,9 @@ macro_rules! define_read {
>          $(#[$attr])*
>          #[inline]
>          pub fn $name(&self, offset: usize) -> $type_name {
> -            let addr =3D self.io_addr_assert::<$type_name>(offset);
> +            let _addr =3D self.io_addr_assert::<$type_name>(offset);
> =20
> -            // SAFETY: By the type invariant `addr` is a valid address f=
or MMIO operations.
> -            unsafe { bindings::$c_fn(addr as *const c_void) }
> +            $call_macro!($c_fn, self, offset, $type_name, _addr).unwrap_=
or(!0)

This introduces unnecessary CPU cycles in the infallible case, I think the
implementations of the try and non-try variants should remain separate.