Messages in this thread | | | Date | Sat, 25 Feb 2023 22:23:40 +0000 | From | Gary Guo <> | Subject | Re: [PATCH 5/5] rust: error: Add from_kernel_result!() macro |
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On Fri, 24 Feb 2023 15:56:05 -0800 Boqun Feng <boqun.feng@gmail.com> wrote:
> On Fri, Feb 24, 2023 at 05:50:23PM +0900, Asahi Lina wrote: > > From: Wedson Almeida Filho <wedsonaf@gmail.com> > > > > Add a helper macro to easily return C result codes from a Rust function > > that calls functions which return a Result<T>. > > > > Lina: Imported from rust-for-linux/rust, originally developed by Wedson > > as part of file_operations.rs. Added the allow() flags since there is no > > user in the kernel crate yet and fixed a typo in a comment. > > > > Co-developed-by: Fox Chen <foxhlchen@gmail.com> > > Signed-off-by: Fox Chen <foxhlchen@gmail.com> > > Co-developed-by: Miguel Ojeda <ojeda@kernel.org> > > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > > Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> > > Signed-off-by: Asahi Lina <lina@asahilina.net> > > --- > > rust/kernel/error.rs | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 52 insertions(+) > > > > diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs > > index cf3d089477d2..8a9222595cd1 100644 > > --- a/rust/kernel/error.rs > > +++ b/rust/kernel/error.rs > > @@ -226,3 +226,55 @@ pub(crate) fn from_kernel_err_ptr<T>(ptr: *mut T) -> Result<*mut T> { > > } > > Ok(ptr) > > } > > + > > +// TODO: Remove `dead_code` marker once an in-kernel client is available. > > +#[allow(dead_code)] > > +pub(crate) fn from_kernel_result_helper<T>(r: Result<T>) -> T > > +where > > + T: From<i16>, > > +{ > > + match r { > > + Ok(v) => v, > > + // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`, > > + // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above, > > + // therefore a negative `errno` always fits in an `i16` and will not overflow. > > + Err(e) => T::from(e.to_kernel_errno() as i16), > > + } > > +} > > + > > +/// Transforms a [`crate::error::Result<T>`] to a kernel C integer result. > > +/// > > +/// This is useful when calling Rust functions that return [`crate::error::Result<T>`] > > +/// from inside `extern "C"` functions that need to return an integer > > +/// error result. > > +/// > > +/// `T` should be convertible from an `i16` via `From<i16>`. > > +/// > > +/// # Examples > > +/// > > +/// ```ignore > > +/// # use kernel::from_kernel_result; > > +/// # use kernel::bindings; > > +/// unsafe extern "C" fn probe_callback( > > +/// pdev: *mut bindings::platform_device, > > +/// ) -> core::ffi::c_int { > > +/// from_kernel_result! { > > +/// let ptr = devm_alloc(pdev)?; > > +/// bindings::platform_set_drvdata(pdev, ptr); > > +/// Ok(0) > > +/// } > > +/// } > > +/// ``` > > +// TODO: Remove `unused_macros` marker once an in-kernel client is available. > > +#[allow(unused_macros)] > > +macro_rules! from_kernel_result { > > This actually doesn't need to be a macro, right? The following function > version: > > pub fn from_kernel_result<T, F>(f: F) -> T > where > T: From<i16>, > F: FnOnce() -> Result<T>; > > is not bad, the above case then can be written as: > > unsafe extern "C" fn probe_callback( > pdev: *mut bindings::platform_device, > ) -> core::ffi::c_int { > from_kernel_result(|| { > let ptr = devm_alloc(pdev)?; > bindings::platform_set_drvdata(pdev, ptr); > Ok(0) > }) > } > > less magical, but the control flow is more clear. > > Thoughts?
I don't think even the closure is necessary? Why not just
pub fn from_kernel_result<T: From<i16>>(r: Result<T>) -> T
and
unsafe extern "C" fn probe_callback( pdev: *mut bindings::platform_device, ) -> core::ffi::c_int { from_kernel_result({ let ptr = devm_alloc(pdev)?; bindings::platform_set_drvdata(pdev, ptr); Ok(0) }) }
?
Best, Gary
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