linux-kernel - Re: [PATCH v2 5/5] panic_qr: use new #[export] macro

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Message-ID: <CAJ-ks9k2HaeTyGfFSfeJUFWkwc2F2hvTg2m4yEQ+8-AvLS6UZg@mail.gmail.com>
Date: Fri, 28 Feb 2025 12:15:07 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 5/5] panic_qr: use new #[export] macro

On Fri, Feb 28, 2025 at 12:08 PM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> On Fri, Feb 28, 2025 at 4:55 PM Tamir Duberstein <tamird@...il.com> wrote:
> >
> > On Fri, Feb 28, 2025 at 7:41 AM Alice Ryhl <aliceryhl@...gle.com> wrote:
> > >
> > > @@ -980,8 +983,12 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) {
> > >  /// * If `url_len` > 0, remove the 2 segments header/length and also count the
> > >  ///   conversion to numeric segments.
> > >  /// * If `url_len` = 0, only removes 3 bytes for 1 binary segment.
> > > -#[no_mangle]
> > > -pub extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {
> > > +///
> > > +/// # Safety
> > > +///
> > > +/// Always safe to call.
> >
> > This should explain why it's marked unsafe, since it's always safe to call.
>
> Safety comments generally do not explain rationale for why they are
> the way they are. Where would you like me to put it?

Safety comments also generally do not say that the function isn't
really unsafe (with a notable exception in
`samples/rust/rust_print_main.rs` which is similar to this case).

Perhaps "This function is marked unsafe because ... but since a safety
comment is still required:" would flow nicely into the safety section.

> > > @@ -36,6 +36,10 @@
> > >  #include <linux/workqueue.h>
> > >  #include <trace/events/rust_sample.h>
> > >
> > > +#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
> > > +#include <drm/drm_panic.h>
> > > +#endif
> >
> > Why the guard here?
> >
> > It'd be nice to have a comment here explaining the atypical need for
> > this include.
>
> It's not necessary. I can drop it.

Ok. A comment on the include would still be helpful.