kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/include/sound/rt5660.h b/include/sound/rt5660.h
new file mode 100644
index 000000000..7e8656cec
--- /dev/null
+++ b/include/sound/rt5660.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * linux/sound/rt5660.h -- Platform data for RT5660
+ *
+ * Copyright 2016 Realtek Semiconductor Corp.
+ * Author: Oder Chiou <oder_chiou@realtek.com>
+ */
+
+#ifndef __LINUX_SND_RT5660_H
+#define __LINUX_SND_RT5660_H
+
+enum rt5660_dmic1_data_pin {
+	RT5660_DMIC1_NULL,
+	RT5660_DMIC1_DATA_GPIO2,
+	RT5660_DMIC1_DATA_IN1P,
+};
+
+struct rt5660_platform_data {
+	/* IN1 & IN3 can optionally be differential */
+	bool in1_diff;
+	bool in3_diff;
+	bool use_ldo2;
+	bool poweroff_codec_in_suspend;
+
+	enum rt5660_dmic1_data_pin dmic1_data_pin;
+};
+
+#endif