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, 67 insertions, 0 deletions

diff --git a/include/sound/designware_i2s.h b/include/sound/designware_i2s.h
new file mode 100644
index 000000000..f6803205a
--- /dev/null
+++ b/include/sound/designware_i2s.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (ST) 2012 Rajeev Kumar (rajeevkumar.linux@gmail.com)
+ */
+
+#ifndef __SOUND_DESIGNWARE_I2S_H
+#define __SOUND_DESIGNWARE_I2S_H
+
+#include <linux/dmaengine.h>
+#include <linux/types.h>
+
+/*
+ * struct i2s_clk_config_data - represent i2s clk configuration data
+ * @chan_nr: number of channel
+ * @data_width: number of bits per sample (8/16/24/32 bit)
+ * @sample_rate: sampling frequency (8Khz, 16Khz, 32Khz, 44Khz, 48Khz)
+ */
+struct i2s_clk_config_data {
+	int chan_nr;
+	u32 data_width;
+	u32 sample_rate;
+};
+
+struct dw_i2s_dev;
+
+struct i2s_platform_data {
+	#define DWC_I2S_PLAY	(1 << 0)
+	#define DWC_I2S_RECORD	(1 << 1)
+	#define DW_I2S_SLAVE	(1 << 2)
+	#define DW_I2S_MASTER	(1 << 3)
+	unsigned int cap;
+	int channel;
+	u32 snd_fmts;
+	u32 snd_rates;
+
+	#define DW_I2S_QUIRK_COMP_REG_OFFSET	(1 << 0)
+	#define DW_I2S_QUIRK_COMP_PARAM1	(1 << 1)
+	#define DW_I2S_QUIRK_16BIT_IDX_OVERRIDE (1 << 2)
+	unsigned int quirks;
+	unsigned int i2s_reg_comp1;
+	unsigned int i2s_reg_comp2;
+
+	void *play_dma_data;
+	void *capture_dma_data;
+	bool (*filter)(struct dma_chan *chan, void *slave);
+	int (*i2s_clk_cfg)(struct i2s_clk_config_data *config);
+	int (*i2s_pd_init)(struct dw_i2s_dev *dev);
+};
+
+struct i2s_dma_data {
+	void *data;
+	dma_addr_t addr;
+	u32 max_burst;
+	enum dma_slave_buswidth addr_width;
+	bool (*filter)(struct dma_chan *chan, void *slave);
+};
+
+/* I2S DMA registers */
+#define I2S_RXDMA		0x01C0
+#define I2S_TXDMA		0x01C8
+
+#define TWO_CHANNEL_SUPPORT	2	/* up to 2.0 */
+#define FOUR_CHANNEL_SUPPORT	4	/* up to 3.1 */
+#define SIX_CHANNEL_SUPPORT	6	/* up to 5.1 */
+#define EIGHT_CHANNEL_SUPPORT	8	/* up to 7.1 */
+
+#endif /*  __SOUND_DESIGNWARE_I2S_H */