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1f9ed17254
In Rust, it is possible to `allow` particular warnings (diagnostics,
lints) locally, making the compiler ignore instances of a given warning
within a given function, module, block, etc.
It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C:
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
static void f(void) {}
#pragma GCC diagnostic pop
But way less verbose:
#[allow(dead_code)]
fn f() {}
By that virtue, it makes it possible to comfortably enable more
diagnostics by default (i.e. outside `W=` levels) that may have some
false positives but that are otherwise quite useful to keep enabled to
catch potential mistakes.
The `#[expect(...)]` attribute [1] takes this further, and makes the
compiler warn if the diagnostic was _not_ produced. For instance, the
following will ensure that, when `f()` is called somewhere, we will have
to remove the attribute:
#[expect(dead_code)]
fn f() {}
If we do not, we get a warning from the compiler:
warning: this lint expectation is unfulfilled
--> x.rs:3:10
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3 | #[expect(dead_code)]
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= note: `#[warn(unfulfilled_lint_expectations)]` on by default
This means that `expect`s do not get forgotten when they are not needed.
See the next commit for more details, nuances on its usage and
documentation on the feature.
The attribute requires the `lint_reasons` [2] unstable feature, but it
is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has
already been useful to clean things up in this patch series, finding
cases where the `allow`s should not have been there.
Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s
where possible.
This feature was also an example of the ongoing collaboration between
Rust and the kernel -- we tested it in the kernel early on and found an
issue that was quickly resolved [3].
Cc: Fridtjof Stoldt <xfrednet@gmail.com>
Cc: Urgau <urgau@numericable.fr>
Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1]
Link: https://github.com/rust-lang/rust/issues/54503 [2]
Link: https://github.com/rust-lang/rust/issues/114557 [3]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Tested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
73 lines
2.0 KiB
Rust
73 lines
2.0 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! `ioctl()` number definitions.
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//!
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//! C header: [`include/asm-generic/ioctl.h`](srctree/include/asm-generic/ioctl.h)
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#![expect(non_snake_case)]
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use crate::build_assert;
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/// Build an ioctl number, analogous to the C macro of the same name.
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#[inline(always)]
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const fn _IOC(dir: u32, ty: u32, nr: u32, size: usize) -> u32 {
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build_assert!(dir <= uapi::_IOC_DIRMASK);
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build_assert!(ty <= uapi::_IOC_TYPEMASK);
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build_assert!(nr <= uapi::_IOC_NRMASK);
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build_assert!(size <= (uapi::_IOC_SIZEMASK as usize));
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(dir << uapi::_IOC_DIRSHIFT)
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| (ty << uapi::_IOC_TYPESHIFT)
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| (nr << uapi::_IOC_NRSHIFT)
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| ((size as u32) << uapi::_IOC_SIZESHIFT)
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}
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/// Build an ioctl number for an argumentless ioctl.
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#[inline(always)]
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pub const fn _IO(ty: u32, nr: u32) -> u32 {
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_IOC(uapi::_IOC_NONE, ty, nr, 0)
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}
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/// Build an ioctl number for a read-only ioctl.
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#[inline(always)]
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pub const fn _IOR<T>(ty: u32, nr: u32) -> u32 {
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_IOC(uapi::_IOC_READ, ty, nr, core::mem::size_of::<T>())
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}
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/// Build an ioctl number for a write-only ioctl.
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#[inline(always)]
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pub const fn _IOW<T>(ty: u32, nr: u32) -> u32 {
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_IOC(uapi::_IOC_WRITE, ty, nr, core::mem::size_of::<T>())
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}
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/// Build an ioctl number for a read-write ioctl.
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#[inline(always)]
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pub const fn _IOWR<T>(ty: u32, nr: u32) -> u32 {
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_IOC(
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uapi::_IOC_READ | uapi::_IOC_WRITE,
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ty,
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nr,
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core::mem::size_of::<T>(),
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)
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}
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/// Get the ioctl direction from an ioctl number.
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pub const fn _IOC_DIR(nr: u32) -> u32 {
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(nr >> uapi::_IOC_DIRSHIFT) & uapi::_IOC_DIRMASK
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}
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/// Get the ioctl type from an ioctl number.
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pub const fn _IOC_TYPE(nr: u32) -> u32 {
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(nr >> uapi::_IOC_TYPESHIFT) & uapi::_IOC_TYPEMASK
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}
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/// Get the ioctl number from an ioctl number.
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pub const fn _IOC_NR(nr: u32) -> u32 {
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(nr >> uapi::_IOC_NRSHIFT) & uapi::_IOC_NRMASK
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}
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/// Get the ioctl size from an ioctl number.
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pub const fn _IOC_SIZE(nr: u32) -> usize {
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((nr >> uapi::_IOC_SIZESHIFT) & uapi::_IOC_SIZEMASK) as usize
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}
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