From: Gary Guo <gary@garyguo.net>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: "Asahi Lina" <lina@asahilina.net>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Sven Van Asbroeck" <thesven73@gmail.com>,
"Fox Chen" <foxhlchen@gmail.com>,
rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
asahi@lists.linux.dev
Subject: Re: [PATCH 5/5] rust: error: Add from_kernel_result!() macro
Date: Sat, 25 Feb 2023 22:23:40 +0000 [thread overview]
Message-ID: <20230225222340.34d749ee.gary@garyguo.net> (raw)
In-Reply-To: <Y/lOlcSpc+d9ytq/@boqun-archlinux>
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
next prev parent reply other threads:[~2023-02-25 22:23 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-24 8:50 [PATCH 0/5] rust: error: Add missing wrappers to convert to/from kernel error codes Asahi Lina
2023-02-24 8:50 ` [PATCH 1/5] rust: error: Add Error::to_ptr() Asahi Lina
2023-02-25 22:14 ` Gary Guo
2023-02-26 14:26 ` Miguel Ojeda
2023-03-07 20:21 ` Miguel Ojeda
2023-02-24 8:50 ` [PATCH 2/5] rust: error: Add Error::from_kernel_errno() Asahi Lina
2023-02-25 22:19 ` Gary Guo
2023-02-26 13:56 ` Miguel Ojeda
2023-02-27 13:27 ` Andreas Hindborg
2023-02-24 8:50 ` [PATCH 3/5] rust: error: Add to_result() helper Asahi Lina
2023-02-27 13:26 ` Andreas Hindborg
2023-02-24 8:50 ` [PATCH 4/5] rust: error: Add a helper to convert a C ERR_PTR to a `Result` Asahi Lina
2023-02-27 13:41 ` Andreas Hindborg
2023-02-27 13:52 ` Miguel Ojeda
2023-02-24 8:50 ` [PATCH 5/5] rust: error: Add from_kernel_result!() macro Asahi Lina
2023-02-24 23:56 ` Boqun Feng
2023-02-25 2:31 ` Asahi Lina
2023-02-25 22:23 ` Gary Guo [this message]
2023-02-26 2:22 ` Boqun Feng
2023-02-26 13:36 ` Gary Guo
2023-02-26 18:16 ` Boqun Feng
2023-02-26 20:59 ` Miguel Ojeda
2023-02-26 22:13 ` Boqun Feng
2023-02-27 12:10 ` Miguel Ojeda
2023-02-27 16:11 ` Boqun Feng
2023-02-27 13:59 ` Martin Rodriguez Reboredo
2023-02-26 13:40 ` Miguel Ojeda
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