Re: module parameters permission

From: Greg KH
Date: Thu Apr 29 2021 - 06:05:14 EST


On Thu, Apr 29, 2021 at 11:58:20AM +0200, Fabio Aiuto wrote:
> 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?

Not at all, use the octal values instead please.

That's the way that we have declared a while ago, and I think
checkpatch.pl will even catch if you try to do this in any new code.
Please don't force us to deal with S_* defines in rust code as well.

thanks,

greg k-h