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, 109 insertions, 0 deletions

diff --git a/include/sound/sdca_interrupts.h b/include/sound/sdca_interrupts.h
new file mode 100644
index 000000000..3b30146e2
--- /dev/null
+++ b/include/sound/sdca_interrupts.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The MIPI SDCA specification is available for public downloads at
+ * https://www.mipi.org/mipi-sdca-v1-0-download
+ *
+ * Copyright (C) 2025 Cirrus Logic, Inc. and
+ *                    Cirrus Logic International Semiconductor Ltd.
+ */
+
+#ifndef __SDCA_INTERRUPTS_H__
+#define __SDCA_INTERRUPTS_H__
+
+#include <linux/interrupt.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+
+struct device;
+struct snd_soc_component;
+struct sdca_function_data;
+
+#define SDCA_MAX_INTERRUPTS 31 /* the last bit is reserved for future extensions */
+
+/**
+ * struct sdca_interrupt - contains information about a single SDCA interrupt
+ * @name: The name of the interrupt.
+ * @dev: Pointer to the Function device.
+ * @device_regmap: Pointer to the IRQ regmap.
+ * @function_regmap: Pointer to the SDCA Function regmap.
+ * @component: Pointer to the ASoC component owns the interrupt.
+ * @function: Pointer to the Function that the interrupt is associated with.
+ * @entity: Pointer to the Entity that the interrupt is associated with.
+ * @control: Pointer to the Control that the interrupt is associated with.
+ * @handler: Handler function to be called for the IRQ.
+ * @priv: Pointer to private data for use by the handler.
+ * @free_priv: Pointer to a function that can be used to free the priv data.
+ * @irq: IRQ number allocated to this interrupt, also used internally to track
+ * the IRQ being assigned.
+ * @early_request: Flag to indicate this IRQ was requested at bus probe time.
+ */
+struct sdca_interrupt {
+	const char *name;
+
+	struct device *dev;
+	struct regmap *device_regmap;
+	struct regmap *function_regmap;
+	struct snd_soc_component *component;
+	struct sdca_function_data *function;
+	struct sdca_entity *entity;
+	struct sdca_control *control;
+	irq_handler_t handler;
+
+	void *priv;
+	void (*free_priv)(struct sdca_interrupt *interrupt);
+
+	int irq;
+	bool early_request;
+};
+
+/**
+ * struct sdca_interrupt_info - contains top-level SDCA interrupt information
+ * @irq_chip: regmap irq chip structure.
+ * @irq_data: regmap irq chip data structure.
+ * @irqs: Array of data for each individual IRQ.
+ * @irq_lock: Protects access to the list of sdca_interrupt structures.
+ */
+struct sdca_interrupt_info {
+	struct regmap_irq_chip irq_chip;
+	struct regmap_irq_chip_data *irq_data;
+
+	struct sdca_interrupt irqs[SDCA_MAX_INTERRUPTS];
+
+	struct mutex irq_lock; /* Protect irqs list across functions */
+};
+
+int sdca_irq_request(struct device *dev, struct sdca_interrupt_info *interrupt_info,
+		     int sdca_irq, const char *name, irq_handler_t handler,
+		     void *data);
+void sdca_irq_free(struct device *dev, struct sdca_interrupt_info *interrupt_info,
+		   int sdca_irq, const char *name, void *data);
+int sdca_irq_data_populate(struct device *dev, struct regmap *function_regmap,
+			   struct snd_soc_component *component,
+			   struct sdca_function_data *function,
+			   struct sdca_entity *entity,
+			   struct sdca_control *control,
+			   struct sdca_interrupt *interrupt);
+int sdca_irq_populate_early(struct device *dev, struct regmap *function_regmap,
+			    struct sdca_function_data *function,
+			    struct sdca_interrupt_info *info);
+int sdca_irq_populate(struct sdca_function_data *function,
+		      struct snd_soc_component *component,
+		      struct sdca_interrupt_info *info);
+void sdca_irq_cleanup(struct device *dev,
+		      struct sdca_function_data *function,
+		      struct sdca_interrupt_info *info);
+void sdca_irq_cleanup_late(struct device *dev,
+			   struct sdca_function_data *function,
+			   struct sdca_interrupt_info *info);
+
+struct sdca_interrupt_info *devm_sdca_irq_allocate(struct device *dev,
+						   struct regmap *regmap, int irq);
+
+void sdca_irq_enable_early(struct sdca_function_data *function,
+			   struct sdca_interrupt_info *info);
+void sdca_irq_enable(struct sdca_function_data *function,
+		     struct sdca_interrupt_info *info);
+void sdca_irq_disable(struct sdca_function_data *function,
+		      struct sdca_interrupt_info *info);
+
+#endif