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, 150 insertions, 0 deletions

diff --git a/include/video/mipi_display.h b/include/video/mipi_display.h
new file mode 100644
index 000000000..b6d8b8742
--- /dev/null
+++ b/include/video/mipi_display.h
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Defines for Mobile Industry Processor Interface (MIPI(R))
+ * Display Working Group standards: DSI, DCS, DBI, DPI
+ *
+ * Copyright (C) 2010 Guennadi Liakhovetski <g.liakhovetski@gmx.de>
+ * Copyright (C) 2006 Nokia Corporation
+ * Author: Imre Deak <imre.deak@nokia.com>
+ */
+#ifndef MIPI_DISPLAY_H
+#define MIPI_DISPLAY_H
+
+/* MIPI DSI Processor-to-Peripheral transaction types */
+enum {
+	MIPI_DSI_V_SYNC_START				= 0x01,
+	MIPI_DSI_V_SYNC_END				= 0x11,
+	MIPI_DSI_H_SYNC_START				= 0x21,
+	MIPI_DSI_H_SYNC_END				= 0x31,
+
+	MIPI_DSI_COMPRESSION_MODE			= 0x07,
+	MIPI_DSI_END_OF_TRANSMISSION			= 0x08,
+
+	MIPI_DSI_COLOR_MODE_OFF				= 0x02,
+	MIPI_DSI_COLOR_MODE_ON				= 0x12,
+	MIPI_DSI_SHUTDOWN_PERIPHERAL			= 0x22,
+	MIPI_DSI_TURN_ON_PERIPHERAL			= 0x32,
+
+	MIPI_DSI_GENERIC_SHORT_WRITE_0_PARAM		= 0x03,
+	MIPI_DSI_GENERIC_SHORT_WRITE_1_PARAM		= 0x13,
+	MIPI_DSI_GENERIC_SHORT_WRITE_2_PARAM		= 0x23,
+
+	MIPI_DSI_GENERIC_READ_REQUEST_0_PARAM		= 0x04,
+	MIPI_DSI_GENERIC_READ_REQUEST_1_PARAM		= 0x14,
+	MIPI_DSI_GENERIC_READ_REQUEST_2_PARAM		= 0x24,
+
+	MIPI_DSI_DCS_SHORT_WRITE			= 0x05,
+	MIPI_DSI_DCS_SHORT_WRITE_PARAM			= 0x15,
+
+	MIPI_DSI_DCS_READ				= 0x06,
+	MIPI_DSI_EXECUTE_QUEUE				= 0x16,
+
+	MIPI_DSI_SET_MAXIMUM_RETURN_PACKET_SIZE		= 0x37,
+
+	MIPI_DSI_NULL_PACKET				= 0x09,
+	MIPI_DSI_BLANKING_PACKET			= 0x19,
+	MIPI_DSI_GENERIC_LONG_WRITE			= 0x29,
+	MIPI_DSI_DCS_LONG_WRITE				= 0x39,
+
+	MIPI_DSI_PICTURE_PARAMETER_SET			= 0x0a,
+	MIPI_DSI_COMPRESSED_PIXEL_STREAM		= 0x0b,
+
+	MIPI_DSI_LOOSELY_PACKED_PIXEL_STREAM_YCBCR20	= 0x0c,
+	MIPI_DSI_PACKED_PIXEL_STREAM_YCBCR24		= 0x1c,
+	MIPI_DSI_PACKED_PIXEL_STREAM_YCBCR16		= 0x2c,
+
+	MIPI_DSI_PACKED_PIXEL_STREAM_30			= 0x0d,
+	MIPI_DSI_PACKED_PIXEL_STREAM_36			= 0x1d,
+	MIPI_DSI_PACKED_PIXEL_STREAM_YCBCR12		= 0x3d,
+
+	MIPI_DSI_PACKED_PIXEL_STREAM_16			= 0x0e,
+	MIPI_DSI_PACKED_PIXEL_STREAM_18			= 0x1e,
+	MIPI_DSI_PIXEL_STREAM_3BYTE_18			= 0x2e,
+	MIPI_DSI_PACKED_PIXEL_STREAM_24			= 0x3e,
+};
+
+/* MIPI DSI Peripheral-to-Processor transaction types */
+enum {
+	MIPI_DSI_RX_ACKNOWLEDGE_AND_ERROR_REPORT	= 0x02,
+	MIPI_DSI_RX_END_OF_TRANSMISSION			= 0x08,
+	MIPI_DSI_RX_GENERIC_SHORT_READ_RESPONSE_1BYTE	= 0x11,
+	MIPI_DSI_RX_GENERIC_SHORT_READ_RESPONSE_2BYTE	= 0x12,
+	MIPI_DSI_RX_GENERIC_LONG_READ_RESPONSE		= 0x1a,
+	MIPI_DSI_RX_DCS_LONG_READ_RESPONSE		= 0x1c,
+	MIPI_DSI_RX_DCS_SHORT_READ_RESPONSE_1BYTE	= 0x21,
+	MIPI_DSI_RX_DCS_SHORT_READ_RESPONSE_2BYTE	= 0x22,
+};
+
+/* MIPI DCS commands */
+enum {
+	MIPI_DCS_NOP			= 0x00,
+	MIPI_DCS_SOFT_RESET		= 0x01,
+	MIPI_DCS_GET_COMPRESSION_MODE	= 0x03,
+	MIPI_DCS_GET_DISPLAY_ID		= 0x04,
+	MIPI_DCS_GET_ERROR_COUNT_ON_DSI	= 0x05,
+	MIPI_DCS_GET_RED_CHANNEL	= 0x06,
+	MIPI_DCS_GET_GREEN_CHANNEL	= 0x07,
+	MIPI_DCS_GET_BLUE_CHANNEL	= 0x08,
+	MIPI_DCS_GET_DISPLAY_STATUS	= 0x09,
+	MIPI_DCS_GET_POWER_MODE		= 0x0A,
+	MIPI_DCS_GET_ADDRESS_MODE	= 0x0B,
+	MIPI_DCS_GET_PIXEL_FORMAT	= 0x0C,
+	MIPI_DCS_GET_DISPLAY_MODE	= 0x0D,
+	MIPI_DCS_GET_SIGNAL_MODE	= 0x0E,
+	MIPI_DCS_GET_DIAGNOSTIC_RESULT	= 0x0F,
+	MIPI_DCS_ENTER_SLEEP_MODE	= 0x10,
+	MIPI_DCS_EXIT_SLEEP_MODE	= 0x11,
+	MIPI_DCS_ENTER_PARTIAL_MODE	= 0x12,
+	MIPI_DCS_ENTER_NORMAL_MODE	= 0x13,
+	MIPI_DCS_GET_IMAGE_CHECKSUM_RGB	= 0x14,
+	MIPI_DCS_GET_IMAGE_CHECKSUM_CT	= 0x15,
+	MIPI_DCS_EXIT_INVERT_MODE	= 0x20,
+	MIPI_DCS_ENTER_INVERT_MODE	= 0x21,
+	MIPI_DCS_SET_GAMMA_CURVE	= 0x26,
+	MIPI_DCS_SET_DISPLAY_OFF	= 0x28,
+	MIPI_DCS_SET_DISPLAY_ON		= 0x29,
+	MIPI_DCS_SET_COLUMN_ADDRESS	= 0x2A,
+	MIPI_DCS_SET_PAGE_ADDRESS	= 0x2B,
+	MIPI_DCS_WRITE_MEMORY_START	= 0x2C,
+	MIPI_DCS_WRITE_LUT		= 0x2D,
+	MIPI_DCS_READ_MEMORY_START	= 0x2E,
+	MIPI_DCS_SET_PARTIAL_ROWS	= 0x30,		/* MIPI DCS 1.02 - MIPI_DCS_SET_PARTIAL_AREA before that */
+	MIPI_DCS_SET_PARTIAL_COLUMNS	= 0x31,
+	MIPI_DCS_SET_SCROLL_AREA	= 0x33,
+	MIPI_DCS_SET_TEAR_OFF		= 0x34,
+	MIPI_DCS_SET_TEAR_ON		= 0x35,
+	MIPI_DCS_SET_ADDRESS_MODE	= 0x36,
+	MIPI_DCS_SET_SCROLL_START	= 0x37,
+	MIPI_DCS_EXIT_IDLE_MODE		= 0x38,
+	MIPI_DCS_ENTER_IDLE_MODE	= 0x39,
+	MIPI_DCS_SET_PIXEL_FORMAT	= 0x3A,
+	MIPI_DCS_WRITE_MEMORY_CONTINUE	= 0x3C,
+	MIPI_DCS_SET_3D_CONTROL		= 0x3D,
+	MIPI_DCS_READ_MEMORY_CONTINUE	= 0x3E,
+	MIPI_DCS_GET_3D_CONTROL		= 0x3F,
+	MIPI_DCS_SET_VSYNC_TIMING	= 0x40,
+	MIPI_DCS_SET_TEAR_SCANLINE	= 0x44,
+	MIPI_DCS_GET_SCANLINE		= 0x45,
+	MIPI_DCS_SET_DISPLAY_BRIGHTNESS = 0x51,		/* MIPI DCS 1.3 */
+	MIPI_DCS_GET_DISPLAY_BRIGHTNESS = 0x52,		/* MIPI DCS 1.3 */
+	MIPI_DCS_WRITE_CONTROL_DISPLAY  = 0x53,		/* MIPI DCS 1.3 */
+	MIPI_DCS_GET_CONTROL_DISPLAY	= 0x54,		/* MIPI DCS 1.3 */
+	MIPI_DCS_WRITE_POWER_SAVE	= 0x55,		/* MIPI DCS 1.3 */
+	MIPI_DCS_GET_POWER_SAVE		= 0x56,		/* MIPI DCS 1.3 */
+	MIPI_DCS_SET_CABC_MIN_BRIGHTNESS = 0x5E,	/* MIPI DCS 1.3 */
+	MIPI_DCS_GET_CABC_MIN_BRIGHTNESS = 0x5F,	/* MIPI DCS 1.3 */
+	MIPI_DCS_READ_DDB_START		= 0xA1,
+	MIPI_DCS_READ_PPS_START		= 0xA2,
+	MIPI_DCS_READ_DDB_CONTINUE	= 0xA8,
+	MIPI_DCS_READ_PPS_CONTINUE	= 0xA9,
+};
+
+/* MIPI DCS pixel formats */
+#define MIPI_DCS_PIXEL_FMT_24BIT	7
+#define MIPI_DCS_PIXEL_FMT_18BIT	6
+#define MIPI_DCS_PIXEL_FMT_16BIT	5
+#define MIPI_DCS_PIXEL_FMT_12BIT	3
+#define MIPI_DCS_PIXEL_FMT_8BIT		2
+#define MIPI_DCS_PIXEL_FMT_3BIT		1
+
+#endif