linux-kernel - Re: [PATCH] rust: device: Replace CString with CStr in property

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Message-ID: <20250118004443.51cc6302.gary@garyguo.net>
Date: Sat, 18 Jan 2025 00:44:43 +0000
From: Gary Guo <gary@...yguo.net>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Danilo Krummrich <dakr@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Alex
 Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin
 <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, Trevor
 Gross <tmgross@...ch.edu>, Rob Herring <robh@...nel.org>, Dirk Behme
 <dirk.behme@...bosch.com>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: device: Replace CString with CStr in
 property_present()

On Thu, 16 Jan 2025 09:25:17 +0100
Alice Ryhl <aliceryhl@...gle.com> wrote:

> On Thu, Jan 16, 2025 at 6:26 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >
> > The property_present() method expects a &CString currently and will work
> > only with heap allocated C strings.
> >
> > In order to make it work with compile-time string constants too, change
> > the argument type to &CStr.
> >
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>  
> 
> One nit below, but either way:
> 
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> 
> > -    pub fn property_present(&self, name: &CString) -> bool {
> > -        // SAFETY: By the invariant of `CString`, `name` is null-terminated.
> > +    pub fn property_present(&self, name: &CStr) -> bool {
> > +        // SAFETY: By the invariant of `CStr`, `name` is null-terminated.
> >          unsafe { bindings::device_property_present(self.as_raw().cast_const(), name.as_ptr() as *const _) }  
> 
> If you use `name.as_char_ptr()` then you don't need the cast.

Isn't the cast not needed anyway with `as_ptr()`?

c_char is unconditionally u8 now so they're now the same.

Best,
Gary

> 
> Alice