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, 140 insertions, 0 deletions

diff --git a/include/sound/hdmi-codec.h b/include/sound/hdmi-codec.h
new file mode 100644
index 000000000..273f4c36f
--- /dev/null
+++ b/include/sound/hdmi-codec.h
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * hdmi-codec.h - HDMI Codec driver API
+ *
+ * Copyright (C) 2014 Texas Instruments Incorporated - https://www.ti.com
+ *
+ * Author: Jyri Sarha <jsarha@ti.com>
+ */
+
+#ifndef __HDMI_CODEC_H__
+#define __HDMI_CODEC_H__
+
+#include <linux/of_graph.h>
+#include <linux/hdmi.h>
+#include <sound/asoundef.h>
+#include <sound/soc.h>
+#include <uapi/sound/asound.h>
+
+/*
+ * Protocol between ASoC cpu-dai and HDMI-encoder
+ */
+struct hdmi_codec_daifmt {
+	enum {
+		HDMI_I2S,
+		HDMI_RIGHT_J,
+		HDMI_LEFT_J,
+		HDMI_DSP_A,
+		HDMI_DSP_B,
+		HDMI_AC97,
+		HDMI_SPDIF,
+	} fmt;
+	unsigned int bit_clk_inv:1;
+	unsigned int frame_clk_inv:1;
+	unsigned int bit_clk_provider:1;
+	unsigned int frame_clk_provider:1;
+	/* bit_fmt could be standard PCM format or
+	 * IEC958 encoded format. ALSA IEC958 plugin will pass
+	 * IEC958_SUBFRAME format to the underneath driver.
+	 */
+	snd_pcm_format_t bit_fmt;
+};
+
+/*
+ * HDMI audio parameters
+ */
+struct hdmi_codec_params {
+	struct hdmi_audio_infoframe cea;
+	struct snd_aes_iec958 iec;
+	int sample_rate;
+	int sample_width;
+	int channels;
+};
+
+typedef void (*hdmi_codec_plugged_cb)(struct device *dev,
+				      bool plugged);
+
+struct hdmi_codec_pdata;
+struct hdmi_codec_ops {
+	/*
+	 * Called when ASoC starts an audio stream setup.
+	 * Optional
+	 */
+	int (*audio_startup)(struct device *dev, void *data);
+
+	/*
+	 * Configures HDMI-encoder for audio stream.
+	 * Having either prepare or hw_params is mandatory.
+	 */
+	int (*hw_params)(struct device *dev, void *data,
+			 struct hdmi_codec_daifmt *fmt,
+			 struct hdmi_codec_params *hparms);
+
+	/*
+	 * Configures HDMI-encoder for audio stream. Can be called
+	 * multiple times for each setup.
+	 *
+	 * Having either prepare or hw_params is mandatory.
+	 */
+	int (*prepare)(struct device *dev, void *data,
+		       struct hdmi_codec_daifmt *fmt,
+		       struct hdmi_codec_params *hparms);
+
+	/*
+	 * Shuts down the audio stream.
+	 * Mandatory
+	 */
+	void (*audio_shutdown)(struct device *dev, void *data);
+
+	/*
+	 * Mute/unmute HDMI audio stream.
+	 * Optional
+	 */
+	int (*mute_stream)(struct device *dev, void *data,
+			   bool enable, int direction);
+
+	/*
+	 * Provides EDID-Like-Data from connected HDMI device.
+	 * Optional
+	 */
+	int (*get_eld)(struct device *dev, void *data,
+		       uint8_t *buf, size_t len);
+
+	/*
+	 * Getting DAI ID
+	 * Optional
+	 */
+	int (*get_dai_id)(struct snd_soc_component *comment,
+			  struct device_node *endpoint,
+			  void *data);
+
+	/*
+	 * Hook callback function to handle connector plug event.
+	 * Optional
+	 */
+	int (*hook_plugged_cb)(struct device *dev, void *data,
+			       hdmi_codec_plugged_cb fn,
+			       struct device *codec_dev);
+};
+
+/* HDMI codec initalization data */
+struct hdmi_codec_pdata {
+	const struct hdmi_codec_ops *ops;
+	u64 i2s_formats;
+	uint i2s:1;
+	uint no_i2s_playback:1;
+	uint no_i2s_capture:1;
+	uint spdif:1;
+	uint no_spdif_playback:1;
+	uint no_spdif_capture:1;
+	uint no_capture_mute:1;
+	int max_i2s_channels;
+	void *data;
+};
+
+struct snd_soc_component;
+struct snd_soc_jack;
+
+#define HDMI_CODEC_DRV_NAME "hdmi-audio-codec"
+
+#endif /* __HDMI_CODEC_H__ */