Subject: linux-next: build failure after merge of the modules tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 4 Nov 2025 15:45:00 +1100

Hi all,

After merging the modules tree, today's linux-next build (x86_64
allmodconfig) failed like this:

error[E0308]: mismatched types
  --> rust/kernel/module_param.rs:75:47
   |
75 |         let new_value = T::try_from_param_arg(arg)?;
   |                         --------------------- ^^^ expected `&BStr`, found `&CStr`
   |                         |
   |                         arguments to this function are incorrect
   |
   = note: expected reference `&BStr`
              found reference `&ffi::CStr`
note: associated function defined here
  --> rust/kernel/module_param.rs:32:8
   |
32 |     fn try_from_param_arg(arg: &BStr) -> Result<Self>;
   |        ^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.

Caused by commit

  0b08fc292842 ("rust: introduce module_param module")

This is some interaction with something later in linux-next - presumably
commit

  3b83f5d5e78a ("rust: replace `CStr` with `core::ffi::CStr`")

from the rust tree.

Hopefully someone can provide a resolution for me tomorrow.

I have used the modules tree from next-20251103 for today.

-- 
Cheers,
Stephen Rothwell