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Date: Mon, 22 Jan 2024 15:12:04 -0800
From: Greg KH <gregkh@linuxfoundation.org>
To: Danilo Krummrich <dakr@redhat.com>
Cc: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com,
	boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com,
	benno.lossin@proton.me, a.hindborg@samsung.com,
	aliceryhl@google.com, rust-for-linux@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rust: str: add to_ascii_{upper,lower}case() to CString
Message-ID: <2024012251-geriatric-morphine-a275@gregkh>
References: <20240122184608.11863-1-dakr@redhat.com>
 <2024012252-attempt-tables-e3fc@gregkh>
 <Za7uampZiG2IP8dE@cassiopeiae>
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On Mon, Jan 22, 2024 at 11:38:34PM +0100, Danilo Krummrich wrote:
> On Mon, Jan 22, 2024 at 11:35:29AM -0800, Greg KH wrote:
> > On Mon, Jan 22, 2024 at 07:45:57PM +0100, Danilo Krummrich wrote:
> > > Add functions to convert a CString to upper- / lowercase assuming all
> > > characters are ASCII encoded.
> > > 
> > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > ---
> > >  rust/kernel/str.rs | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> > > index 7d848b83add4..d21151d89861 100644
> > > --- a/rust/kernel/str.rs
> > > +++ b/rust/kernel/str.rs
> > > @@ -581,6 +581,16 @@ pub fn try_from_fmt(args: fmt::Arguments<'_>) -> Result<Self, Error> {
> > >          // exist in the buffer.
> > >          Ok(Self { buf })
> > >      }
> > > +
> > > +    /// Converts the whole CString to lowercase.
> > > +    pub fn to_ascii_lowercase(&mut self) {
> > > +        self.buf.make_ascii_lowercase();
> > > +    }
> > > +
> > > +    /// Converts the whole CString to uppercase.
> > > +    pub fn to_ascii_uppercase(&mut self) {
> > > +        self.buf.make_ascii_uppercase();
> > > +    }
> > 
> > How are you handling locales?
> 
> For ASCII only? Not at all, I guess.

Ah, this is ascii, yes, sorry.  So this is a replacement of
toupper()/tolower() in the C api?

> However, std::slice::make_ascii_{lower,upper]case() doesn't seem to handle the
> extended range, which tolower() / toupper(), according to _ctype[], does. Do
> you mean that?

You should support whatever those functions in the kernel support today,
otherwise why add it?  And why not just call the kernel function to be
sure?

thanks,

greg k-h