linux-kernel - Re: [PATCH 03/10] device property: Add fwnode_property_read_int

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Message-ID: <CAL_JsqLCa8AjwsUpS-N9FWymG67w7DjmmBZCKW7G7BAfY78vWw@mail.gmail.com>
Date: Thu, 3 Apr 2025 13:48:19 -0500
From: Rob Herring <robh@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Miguel Ojeda <ojeda@...nel.org>
Cc: Remo Senekowitsch <remo@...nzli.dev>, Daniel Scally <djrscally@...il.com>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Dirk Behme <dirk.behme@...bosch.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
	Alex Gaynor <alex.gaynor@...il.com>, 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>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, linux-kernel@...r.kernel.org, 
	linux-acpi@...r.kernel.org, devicetree@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 03/10] device property: Add fwnode_property_read_int_array()

On Thu, Apr 3, 2025 at 12:55 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Thu, Apr 03, 2025 at 11:36:38AM -0500, Rob Herring wrote:
> > On Thu, Apr 3, 2025 at 11:15 AM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Thu, Apr 03, 2025 at 11:04:32AM -0500, Rob Herring wrote:
> > > > On Thu, Mar 27, 2025 at 3:41 AM Andy Shevchenko
> > > > <andriy.shevchenko@...ux.intel.com> wrote:
> > > > > On Wed, Mar 26, 2025 at 06:13:42PM +0100, Remo Senekowitsch wrote:
> > > > > > The rust bindings for reading device properties has a single
> > > > > > implementation supporting differing sizes of integers. The fwnode C API
> > > > > > already has a similar interface, but it is not exposed with the
> > > > > > fwnode_property_ API. Add the fwnode_property_read_int_array() wrapper.
>
> ...
>
> > > > > > +EXPORT_SYMBOL_GPL(fwnode_property_read_int_array);
> > > > >
> > > > > I'm not sure about this. We have a lot of assumptions in the code that the
> > > > > arrays beneath are only represented by the selected number of integer types.
> > > > > This opens a Pandora's box, e.g., reading in u24, which is not supported by
> > > > > the upper layers..
> > > >
> > > > We can probably drop the export if it is just that which you object to.
> > >
> > > Yes, this is main point, but dropping it does not prevent from still using in
> > > the complied-in code. Is it possible to hide it better?
> >
> > Don't put any declaration in the header and declare it in the rust
> > code? But lack of declaration generates warnings.
>
> Exactly. And I believe we have the typed versions of int_array for a reason.
> Otherwise what's the point in having them to begin with?
> (The first what comes to my mind is a compile time type checking, so we don't
>  try to load u8 with u32 data or any other dirty tricks.)
>
> Maybe it deserves a header that can be included explicitly in the rust stuff
> and being checked at compile time to avoid people using that? Can we achieve
> something like C preprocessor
>
> #ifndef FOO
> #error This header must not be included directly
> #endif

Looks there are RUST_BINDGEN or __BINDGEN__ define which could be used
here. Don't need a header, just wrap the declaration. No idea which
one would be preferred as there's exactly 1 use of each. Miguel?

Rob