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, 310 insertions, 0 deletions

diff --git a/drivers/input/misc/drv2665.c b/drivers/input/misc/drv2665.c
new file mode 100644
index 000000000..4f8c1f69a
--- /dev/null
+++ b/drivers/input/misc/drv2665.c
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * DRV2665 haptics driver family
+ *
+ * Author: Dan Murphy <dmurphy@ti.com>
+ *
+ * Copyright: (C) 2015 Texas Instruments, Inc.
+ */
+
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/regulator/consumer.h>
+
+/* Control registers */
+#define DRV2665_STATUS	0x00
+#define DRV2665_CTRL_1	0x01
+#define DRV2665_CTRL_2	0x02
+#define DRV2665_FIFO	0x0b
+
+/* Status Register */
+#define DRV2665_FIFO_FULL		BIT(0)
+#define DRV2665_FIFO_EMPTY		BIT(1)
+
+/* Control 1 Register */
+#define DRV2665_25_VPP_GAIN		0x00
+#define DRV2665_50_VPP_GAIN		0x01
+#define DRV2665_75_VPP_GAIN		0x02
+#define DRV2665_100_VPP_GAIN		0x03
+#define DRV2665_DIGITAL_IN		0xfc
+#define DRV2665_ANALOG_IN		BIT(2)
+
+/* Control 2 Register */
+#define DRV2665_BOOST_EN		BIT(1)
+#define DRV2665_STANDBY			BIT(6)
+#define DRV2665_DEV_RST			BIT(7)
+#define DRV2665_5_MS_IDLE_TOUT		0x00
+#define DRV2665_10_MS_IDLE_TOUT		0x04
+#define DRV2665_15_MS_IDLE_TOUT		0x08
+#define DRV2665_20_MS_IDLE_TOUT		0x0c
+
+/**
+ * struct drv2665_data -
+ * @input_dev: Pointer to the input device
+ * @client: Pointer to the I2C client
+ * @regmap: Register map of the device
+ * @work: Work item used to off load the enable/disable of the vibration
+ * @regulator: Pointer to the regulator for the IC
+ */
+struct drv2665_data {
+	struct input_dev *input_dev;
+	struct i2c_client *client;
+	struct regmap *regmap;
+	struct work_struct work;
+	struct regulator *regulator;
+};
+
+/* 8kHz Sine wave to stream to the FIFO */
+static const u8 drv2665_sine_wave_form[] = {
+	0x00, 0x10, 0x20, 0x2e, 0x3c, 0x48, 0x53, 0x5b, 0x61, 0x65, 0x66,
+	0x65, 0x61, 0x5b, 0x53, 0x48, 0x3c, 0x2e, 0x20, 0x10,
+	0x00, 0xf0, 0xe0, 0xd2, 0xc4, 0xb8, 0xad, 0xa5, 0x9f, 0x9b, 0x9a,
+	0x9b, 0x9f, 0xa5, 0xad, 0xb8, 0xc4, 0xd2, 0xe0, 0xf0, 0x00,
+};
+
+static const struct reg_default drv2665_reg_defs[] = {
+	{ DRV2665_STATUS, 0x02 },
+	{ DRV2665_CTRL_1, 0x28 },
+	{ DRV2665_CTRL_2, 0x40 },
+	{ DRV2665_FIFO, 0x00 },
+};
+
+static void drv2665_worker(struct work_struct *work)
+{
+	struct drv2665_data *haptics =
+				container_of(work, struct drv2665_data, work);
+	unsigned int read_buf;
+	int error;
+
+	error = regmap_read(haptics->regmap, DRV2665_STATUS, &read_buf);
+	if (error) {
+		dev_err(&haptics->client->dev,
+			"Failed to read status: %d\n", error);
+		return;
+	}
+
+	if (read_buf & DRV2665_FIFO_EMPTY) {
+		error = regmap_bulk_write(haptics->regmap,
+					  DRV2665_FIFO,
+					  drv2665_sine_wave_form,
+					  ARRAY_SIZE(drv2665_sine_wave_form));
+		if (error) {
+			dev_err(&haptics->client->dev,
+				"Failed to write FIFO: %d\n", error);
+			return;
+		}
+	}
+}
+
+static int drv2665_haptics_play(struct input_dev *input, void *data,
+				struct ff_effect *effect)
+{
+	struct drv2665_data *haptics = input_get_drvdata(input);
+
+	schedule_work(&haptics->work);
+
+	return 0;
+}
+
+static void drv2665_close(struct input_dev *input)
+{
+	struct drv2665_data *haptics = input_get_drvdata(input);
+	int error;
+
+	cancel_work_sync(&haptics->work);
+
+	error = regmap_update_bits(haptics->regmap, DRV2665_CTRL_2,
+				   DRV2665_STANDBY, DRV2665_STANDBY);
+	if (error)
+		dev_err(&haptics->client->dev,
+			"Failed to enter standby mode: %d\n", error);
+}
+
+static const struct reg_sequence drv2665_init_regs[] = {
+	{ DRV2665_CTRL_2, 0 | DRV2665_10_MS_IDLE_TOUT },
+	{ DRV2665_CTRL_1, DRV2665_25_VPP_GAIN },
+};
+
+static int drv2665_init(struct drv2665_data *haptics)
+{
+	int error;
+
+	error = regmap_register_patch(haptics->regmap,
+				      drv2665_init_regs,
+				      ARRAY_SIZE(drv2665_init_regs));
+	if (error) {
+		dev_err(&haptics->client->dev,
+			"Failed to write init registers: %d\n",
+			error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct regmap_config drv2665_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = DRV2665_FIFO,
+	.reg_defaults = drv2665_reg_defs,
+	.num_reg_defaults = ARRAY_SIZE(drv2665_reg_defs),
+	.cache_type = REGCACHE_NONE,
+};
+
+static int drv2665_probe(struct i2c_client *client)
+{
+	struct drv2665_data *haptics;
+	int error;
+
+	haptics = devm_kzalloc(&client->dev, sizeof(*haptics), GFP_KERNEL);
+	if (!haptics)
+		return -ENOMEM;
+
+	haptics->regulator = devm_regulator_get(&client->dev, "vbat");
+	if (IS_ERR(haptics->regulator)) {
+		error = PTR_ERR(haptics->regulator);
+		dev_err(&client->dev,
+			"unable to get regulator, error: %d\n", error);
+		return error;
+	}
+
+	haptics->input_dev = devm_input_allocate_device(&client->dev);
+	if (!haptics->input_dev) {
+		dev_err(&client->dev, "Failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	haptics->input_dev->name = "drv2665:haptics";
+	haptics->input_dev->dev.parent = client->dev.parent;
+	haptics->input_dev->close = drv2665_close;
+	input_set_drvdata(haptics->input_dev, haptics);
+	input_set_capability(haptics->input_dev, EV_FF, FF_RUMBLE);
+
+	error = input_ff_create_memless(haptics->input_dev, NULL,
+					drv2665_haptics_play);
+	if (error) {
+		dev_err(&client->dev, "input_ff_create() failed: %d\n",
+			error);
+		return error;
+	}
+
+	INIT_WORK(&haptics->work, drv2665_worker);
+
+	haptics->client = client;
+	i2c_set_clientdata(client, haptics);
+
+	haptics->regmap = devm_regmap_init_i2c(client, &drv2665_regmap_config);
+	if (IS_ERR(haptics->regmap)) {
+		error = PTR_ERR(haptics->regmap);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			error);
+		return error;
+	}
+
+	error = drv2665_init(haptics);
+	if (error) {
+		dev_err(&client->dev, "Device init failed: %d\n", error);
+		return error;
+	}
+
+	error = input_register_device(haptics->input_dev);
+	if (error) {
+		dev_err(&client->dev, "couldn't register input device: %d\n",
+			error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int drv2665_suspend(struct device *dev)
+{
+	struct drv2665_data *haptics = dev_get_drvdata(dev);
+	int error;
+
+	guard(mutex)(&haptics->input_dev->mutex);
+
+	if (input_device_enabled(haptics->input_dev)) {
+		error = regmap_update_bits(haptics->regmap, DRV2665_CTRL_2,
+					   DRV2665_STANDBY, DRV2665_STANDBY);
+		if (error) {
+			dev_err(dev, "Failed to set standby mode\n");
+			regulator_disable(haptics->regulator);
+			return error;
+		}
+
+		error = regulator_disable(haptics->regulator);
+		if (error) {
+			dev_err(dev, "Failed to disable regulator\n");
+			regmap_update_bits(haptics->regmap,
+					   DRV2665_CTRL_2,
+					   DRV2665_STANDBY, 0);
+			return error;
+		}
+	}
+
+	return 0;
+}
+
+static int drv2665_resume(struct device *dev)
+{
+	struct drv2665_data *haptics = dev_get_drvdata(dev);
+	int error;
+
+	guard(mutex)(&haptics->input_dev->mutex);
+
+	if (input_device_enabled(haptics->input_dev)) {
+		error = regulator_enable(haptics->regulator);
+		if (error) {
+			dev_err(dev, "Failed to enable regulator\n");
+			return error;
+		}
+
+		error = regmap_update_bits(haptics->regmap, DRV2665_CTRL_2,
+					   DRV2665_STANDBY, 0);
+		if (error) {
+			dev_err(dev, "Failed to unset standby mode\n");
+			regulator_disable(haptics->regulator);
+			return error;
+		}
+
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(drv2665_pm_ops, drv2665_suspend, drv2665_resume);
+
+static const struct i2c_device_id drv2665_id[] = {
+	{ .name = "drv2665" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, drv2665_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id drv2665_of_match[] = {
+	{ .compatible = "ti,drv2665", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, drv2665_of_match);
+#endif
+
+static struct i2c_driver drv2665_driver = {
+	.probe		= drv2665_probe,
+	.driver		= {
+		.name	= "drv2665-haptics",
+		.of_match_table = of_match_ptr(drv2665_of_match),
+		.pm	= pm_sleep_ptr(&drv2665_pm_ops),
+	},
+	.id_table = drv2665_id,
+};
+module_i2c_driver(drv2665_driver);
+
+MODULE_DESCRIPTION("TI DRV2665 haptics driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dan Murphy <dmurphy@ti.com>");