FAILED: patch "[PATCH] rust: kbuild: give `--config-path` to `rustfmt` in `.rsi`" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x af20ae33e7dd949f2e770198e74ac8f058cb299d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026020314-retool-immobile-ceeb@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From af20ae33e7dd949f2e770198e74ac8f058cb299d Mon Sep 17 00:00:00 2001
From: Miguel Ojeda <[email protected]>
Date: Thu, 15 Jan 2026 19:38:32 +0100
Subject: [PATCH] rust: kbuild: give --config-path to rustfmt in .rsi
target

rustfmt is configured via the .rustfmt.toml file in the source tree, and we apply rustfmt to the macro expanded sources generated by the .rsi target.

However, under an O= pointing to an external folder (i.e. not just a subdir), rustfmt will not find the file when checking the parent folders. Since the edition is configured in this file, this can lead to errors when it encounters newer syntax, e.g.

    error: expected one of `!`, `.`, `::`, `;`, `?`, `where`, `{`, or an operator, found `"rust_minimal"`
      --> samples/rust/rust_minimal.rsi:29:49
       |
    28 | impl ::kernel::ModuleMetadata for RustMinimal {
       |                                               - while parsing this item list starting here
    29 |     const NAME: &'static ::kernel::str::CStr = c"rust_minimal";
       |                                                 ^^^^^^^^^^^^^^ expected one of 8 possible tokens
    30 | }
       | - the item list ends here
       |
       = note: you may be trying to write a c-string literal
       = note: c-string literals require Rust 2021 or later
       = help: pass `--edition 2024` to `rustc`
       = note: for more on editions, read https://doc.rust-lang.org/edition-guide

A workaround is to use RUSTFMT=n, which is documented in the Makefile help for cases where macro expanded source may happen to break rustfmt for other reasons, but this is not one of those cases.

One solution would be to pass --edition, but we want rustfmt to use the entire configuration, even if currently we essentially use the default configuration.

Thus explicitly give the path to the config file to rustfmt instead.

Reported-by Alice Ryhl <[email protected]>

Fixes 2f7ab1267dc9 ("Kbuild: add Rust support")

Cc [email protected]

Reviewed-by Nathan Chancellor <[email protected]>

Reviewed-by Gary Guo <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Miguel Ojeda <[email protected]>

scripts/Makefile.build +1 -1

index 5037f4715d74..0c838c467c76 100644
@@ -356,7 +356,7 @@ $(obj)/%.o: $(obj)/%.rs FORCE
 quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
       cmd_rustc_rsi_rs = \
 	$(rust_common_cmd) -Zunpretty=expanded $< >$@; \
-	command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) $@
+	command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) --config-path $(srctree)/.rustfmt.toml $@
 
 $(obj)/%.rsi: $(obj)/%.rs FORCE
 	+$(call if_changed_dep,rustc_rsi_rs)