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, 116 insertions, 0 deletions

diff --git a/include/media/tveeprom.h b/include/media/tveeprom.h
new file mode 100644
index 000000000..f37c9b15f
--- /dev/null
+++ b/include/media/tveeprom.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * tveeprom - Contains structures and functions to work with Hauppauge
+ *	      eeproms.
+ */
+
+#include <uapi/linux/if_ether.h>
+
+/**
+ * enum tveeprom_audio_processor - Specifies the type of audio processor
+ *				   used on a Hauppauge device.
+ *
+ * @TVEEPROM_AUDPROC_NONE:	No audio processor present
+ * @TVEEPROM_AUDPROC_INTERNAL:	The audio processor is internal to the
+ *				video processor
+ * @TVEEPROM_AUDPROC_MSP:	The audio processor is a MSPXXXX device
+ * @TVEEPROM_AUDPROC_OTHER:	The audio processor is another device
+ */
+enum tveeprom_audio_processor {
+	TVEEPROM_AUDPROC_NONE,
+	TVEEPROM_AUDPROC_INTERNAL,
+	TVEEPROM_AUDPROC_MSP,
+	TVEEPROM_AUDPROC_OTHER,
+};
+
+/**
+ * struct tveeprom - Contains the fields parsed from Hauppauge eeproms
+ *
+ * @has_radio:			1 if the device has radio; 0 otherwise.
+ *
+ * @has_ir:			If has_ir == 0, then it is unknown what the IR
+ *				capabilities are. Otherwise:
+ *				bit 0) 1 (= IR capabilities are known);
+ *				bit 1) IR receiver present;
+ *				bit 2) IR transmitter (blaster) present.
+ *
+ * @has_MAC_address:		0: no MAC, 1: MAC present, 2: unknown.
+ * @tuner_type:			type of the tuner (TUNER_*, as defined at
+ *				include/media/tuner.h).
+ *
+ * @tuner_formats:		Supported analog TV standards (V4L2_STD_*).
+ * @tuner_hauppauge_model:	Hauppauge's code for the device model number.
+ * @tuner2_type:		type of the second tuner (TUNER_*, as defined
+ *				at include/media/tuner.h).
+ *
+ * @tuner2_formats:		Tuner 2 supported analog TV standards
+ *				(V4L2_STD_*).
+ *
+ * @tuner2_hauppauge_model:	tuner 2 Hauppauge's code for the device model
+ *				number.
+ *
+ * @audio_processor:		analog audio decoder, as defined by enum
+ *				tveeprom_audio_processor.
+ *
+ * @decoder_processor:		Hauppauge's code for the decoder chipset.
+ *				Unused by the drivers, as they probe the
+ *				decoder based on the PCI or USB ID.
+ *
+ * @model:			Hauppauge's model number
+ *
+ * @revision:			Card revision number
+ *
+ * @serial_number:		Card's serial number
+ *
+ * @rev_str:			Card revision converted to number
+ *
+ * @MAC_address:		MAC address for the network interface
+ */
+struct tveeprom {
+	u32 has_radio;
+	u32 has_ir;
+	u32 has_MAC_address;
+
+	u32 tuner_type;
+	u32 tuner_formats;
+	u32 tuner_hauppauge_model;
+
+	u32 tuner2_type;
+	u32 tuner2_formats;
+	u32 tuner2_hauppauge_model;
+
+	u32 audio_processor;
+	u32 decoder_processor;
+
+	u32 model;
+	u32 revision;
+	u32 serial_number;
+	char rev_str[5];
+	u8 MAC_address[ETH_ALEN];
+};
+
+/**
+ * tveeprom_hauppauge_analog - Fill struct tveeprom using the contents
+ *			       of the eeprom previously filled at
+ *			       @eeprom_data field.
+ *
+ * @tvee:		Struct to where the eeprom parsed data will be filled;
+ * @eeprom_data:	Array with the contents of the eeprom_data. It should
+ *			contain 256 bytes filled with the contents of the
+ *			eeprom read from the Hauppauge device.
+ */
+void tveeprom_hauppauge_analog(struct tveeprom *tvee,
+			       unsigned char *eeprom_data);
+
+/**
+ * tveeprom_read - Reads the contents of the eeprom found at the Hauppauge
+ *		   devices.
+ *
+ * @c:		I2C client struct
+ * @eedata:	Array where the eeprom content will be stored.
+ * @len:	Size of @eedata array. If the eeprom content will be latter
+ *		be parsed by tveeprom_hauppauge_analog(), len should be, at
+ *		least, 256.
+ */
+int tveeprom_read(struct i2c_client *c, unsigned char *eedata, int len);