linux-kernel - module parameters permission

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Date:   Thu, 29 Apr 2021 11:58:20 +0200
From:   Fabio Aiuto <fabioaiuto83@...il.com>
To:     rust-for-linux@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: module parameters permission

Hi all,

I'm trying to declare module parameters this way:


   params: {
        scull_major: i32 {
            default: 0,
            permissions: bindings::S_IRUGO as i32,
            description: b"Major number",
        },
        scull_minor: i32 {
            default: 0,
            permissions: bindings::S_IRUGO as i32,
            description: b"Minor number",
        },

i.e. using S_IRUGO macro exposed by bindgen. But I have the
following compiler error:

error: proc macro panicked
  --> samples/rust/rust_scull.rs:12:1
   |
12 | / module! {
13 | |     type: RustScull,
14 | |     name: b"rust_scull",
15 | |     author: b"Alessandro Rubini, Jonathan Corbet",
...  |
44 | |     },
45 | | }
   | |_^
   |
   = help: message: Expected Literal

the same if I remove as i32 casts.

if I write permissions as in samples/rust/rust_module_parameters.rs

    params: {
        my_bool: bool {
            default: true,
            permissions: 0,
            description: b"Example of bool",
        },
        my_i32: i32 {
            default: 42,
            permissions: 0o644, <-------
            description: b"Example of i32",
        },

I get no error.

What's the right way to use S_I*UGO macros?

my includes are:

// SPDX-License-Identifier: GPL-2.0

//! Scull driver sample

#![no_std]
#![feature(allocator_api, global_asm)]

use kernel::prelude::*;
use kernel::{chrdev, cstr};
use crate::bindings;

thank you,

fabio