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, 366 insertions, 0 deletions

diff --git a/drivers/input/keyboard/tm2-touchkey.c b/drivers/input/keyboard/tm2-touchkey.c
new file mode 100644
index 000000000..967bbe553
--- /dev/null
+++ b/drivers/input/keyboard/tm2-touchkey.c
@@ -0,0 +1,366 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TM2 touchkey device driver
+ *
+ * Copyright 2005 Phil Blundell
+ * Copyright 2016 Samsung Electronics Co., Ltd.
+ *
+ * Author: Beomho Seo <beomho.seo@samsung.com>
+ * Author: Jaechul Lee <jcsing.lee@samsung.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+
+#define TM2_TOUCHKEY_DEV_NAME		"tm2-touchkey"
+
+#define ARIES_TOUCHKEY_CMD_LED_ON	0x1
+#define ARIES_TOUCHKEY_CMD_LED_OFF	0x2
+#define TM2_TOUCHKEY_CMD_LED_ON		0x10
+#define TM2_TOUCHKEY_CMD_LED_OFF	0x20
+#define TM2_TOUCHKEY_BIT_PRESS_EV	BIT(3)
+#define TM2_TOUCHKEY_BIT_KEYCODE	GENMASK(2, 0)
+#define TM2_TOUCHKEY_LED_VOLTAGE_MIN	2500000
+#define TM2_TOUCHKEY_LED_VOLTAGE_MAX	3300000
+
+struct touchkey_variant {
+	u8 keycode_reg;
+	u8 base_reg;
+	u8 cmd_led_on;
+	u8 cmd_led_off;
+	bool no_reg;
+	bool fixed_regulator;
+};
+
+struct tm2_touchkey_data {
+	struct i2c_client *client;
+	struct input_dev *input_dev;
+	struct led_classdev led_dev;
+	struct regulator *vdd;
+	struct regulator_bulk_data regulators[3];
+	const struct touchkey_variant *variant;
+	u32 keycodes[4];
+	int num_keycodes;
+};
+
+static const struct touchkey_variant tm2_touchkey_variant = {
+	.keycode_reg = 0x03,
+	.base_reg = 0x00,
+	.cmd_led_on = TM2_TOUCHKEY_CMD_LED_ON,
+	.cmd_led_off = TM2_TOUCHKEY_CMD_LED_OFF,
+};
+
+static const struct touchkey_variant midas_touchkey_variant = {
+	.keycode_reg = 0x00,
+	.base_reg = 0x00,
+	.cmd_led_on = TM2_TOUCHKEY_CMD_LED_ON,
+	.cmd_led_off = TM2_TOUCHKEY_CMD_LED_OFF,
+};
+
+static struct touchkey_variant aries_touchkey_variant = {
+	.no_reg = true,
+	.fixed_regulator = true,
+	.cmd_led_on = ARIES_TOUCHKEY_CMD_LED_ON,
+	.cmd_led_off = ARIES_TOUCHKEY_CMD_LED_OFF,
+};
+
+static const struct touchkey_variant tc360_touchkey_variant = {
+	.keycode_reg = 0x00,
+	.base_reg = 0x00,
+	.fixed_regulator = true,
+	.cmd_led_on = TM2_TOUCHKEY_CMD_LED_ON,
+	.cmd_led_off = TM2_TOUCHKEY_CMD_LED_OFF,
+};
+
+static int tm2_touchkey_led_brightness_set(struct led_classdev *led_dev,
+					    enum led_brightness brightness)
+{
+	struct tm2_touchkey_data *touchkey =
+		container_of(led_dev, struct tm2_touchkey_data, led_dev);
+	u32 volt;
+	u8 data;
+
+	if (brightness == LED_OFF) {
+		volt = TM2_TOUCHKEY_LED_VOLTAGE_MIN;
+		data = touchkey->variant->cmd_led_off;
+	} else {
+		volt = TM2_TOUCHKEY_LED_VOLTAGE_MAX;
+		data = touchkey->variant->cmd_led_on;
+	}
+
+	if (!touchkey->variant->fixed_regulator)
+		regulator_set_voltage(touchkey->vdd, volt, volt);
+
+	return touchkey->variant->no_reg ?
+		i2c_smbus_write_byte(touchkey->client, data) :
+		i2c_smbus_write_byte_data(touchkey->client,
+					  touchkey->variant->base_reg, data);
+}
+
+static int tm2_touchkey_power_enable(struct tm2_touchkey_data *touchkey)
+{
+	int error;
+
+	error = regulator_bulk_enable(ARRAY_SIZE(touchkey->regulators),
+				      touchkey->regulators);
+	if (error)
+		return error;
+
+	/* waiting for device initialization, at least 150ms */
+	msleep(150);
+
+	return 0;
+}
+
+static void tm2_touchkey_power_disable(void *data)
+{
+	struct tm2_touchkey_data *touchkey = data;
+
+	regulator_bulk_disable(ARRAY_SIZE(touchkey->regulators),
+			       touchkey->regulators);
+}
+
+static irqreturn_t tm2_touchkey_irq_handler(int irq, void *devid)
+{
+	struct tm2_touchkey_data *touchkey = devid;
+	int data;
+	int index;
+	int i;
+
+	if (touchkey->variant->no_reg)
+		data = i2c_smbus_read_byte(touchkey->client);
+	else
+		data = i2c_smbus_read_byte_data(touchkey->client,
+						touchkey->variant->keycode_reg);
+	if (data < 0) {
+		dev_err(&touchkey->client->dev,
+			"failed to read i2c data: %d\n", data);
+		goto out;
+	}
+
+	index = (data & TM2_TOUCHKEY_BIT_KEYCODE) - 1;
+	if (index < 0 || index >= touchkey->num_keycodes) {
+		dev_warn(&touchkey->client->dev,
+			 "invalid keycode index %d\n", index);
+		goto out;
+	}
+
+	input_event(touchkey->input_dev, EV_MSC, MSC_SCAN, index);
+
+	if (data & TM2_TOUCHKEY_BIT_PRESS_EV) {
+		for (i = 0; i < touchkey->num_keycodes; i++)
+			input_report_key(touchkey->input_dev,
+					 touchkey->keycodes[i], 0);
+	} else {
+		input_report_key(touchkey->input_dev,
+				 touchkey->keycodes[index], 1);
+	}
+
+	input_sync(touchkey->input_dev);
+
+out:
+	if (touchkey->variant->fixed_regulator &&
+				data & TM2_TOUCHKEY_BIT_PRESS_EV) {
+		/* touch turns backlight on, so make sure we're in sync */
+		if (touchkey->led_dev.brightness == LED_OFF)
+			tm2_touchkey_led_brightness_set(&touchkey->led_dev,
+							LED_OFF);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int tm2_touchkey_probe(struct i2c_client *client)
+{
+	struct device_node *np = client->dev.of_node;
+	struct tm2_touchkey_data *touchkey;
+	int error;
+	int i;
+
+	if (!i2c_check_functionality(client->adapter,
+			I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_BYTE_DATA)) {
+		dev_err(&client->dev, "incompatible I2C adapter\n");
+		return -EIO;
+	}
+
+	touchkey = devm_kzalloc(&client->dev, sizeof(*touchkey), GFP_KERNEL);
+	if (!touchkey)
+		return -ENOMEM;
+
+	touchkey->client = client;
+	i2c_set_clientdata(client, touchkey);
+
+	touchkey->variant = of_device_get_match_data(&client->dev);
+
+	touchkey->regulators[0].supply = "vcc";
+	touchkey->regulators[1].supply = "vdd";
+	touchkey->regulators[2].supply = "vddio";
+	error = devm_regulator_bulk_get(&client->dev,
+					ARRAY_SIZE(touchkey->regulators),
+					touchkey->regulators);
+	if (error) {
+		dev_err(&client->dev, "failed to get regulators: %d\n", error);
+		return error;
+	}
+
+	/* Save VDD for easy access */
+	touchkey->vdd = touchkey->regulators[1].consumer;
+
+	touchkey->num_keycodes = of_property_read_variable_u32_array(np,
+					"linux,keycodes", touchkey->keycodes, 0,
+					ARRAY_SIZE(touchkey->keycodes));
+	if (touchkey->num_keycodes <= 0) {
+		/* default keycodes */
+		touchkey->keycodes[0] = KEY_PHONE;
+		touchkey->keycodes[1] = KEY_BACK;
+		touchkey->num_keycodes = 2;
+	}
+
+	error = tm2_touchkey_power_enable(touchkey);
+	if (error) {
+		dev_err(&client->dev, "failed to power up device: %d\n", error);
+		return error;
+	}
+
+	error = devm_add_action_or_reset(&client->dev,
+					 tm2_touchkey_power_disable, touchkey);
+	if (error) {
+		dev_err(&client->dev,
+			"failed to install poweroff handler: %d\n", error);
+		return error;
+	}
+
+	/* input device */
+	touchkey->input_dev = devm_input_allocate_device(&client->dev);
+	if (!touchkey->input_dev) {
+		dev_err(&client->dev, "failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	touchkey->input_dev->name = TM2_TOUCHKEY_DEV_NAME;
+	touchkey->input_dev->id.bustype = BUS_I2C;
+
+	touchkey->input_dev->keycode = touchkey->keycodes;
+	touchkey->input_dev->keycodemax = touchkey->num_keycodes;
+	touchkey->input_dev->keycodesize = sizeof(touchkey->keycodes[0]);
+
+	input_set_capability(touchkey->input_dev, EV_MSC, MSC_SCAN);
+	for (i = 0; i < touchkey->num_keycodes; i++)
+		input_set_capability(touchkey->input_dev, EV_KEY,
+				     touchkey->keycodes[i]);
+
+	error = input_register_device(touchkey->input_dev);
+	if (error) {
+		dev_err(&client->dev,
+			"failed to register input device: %d\n", error);
+		return error;
+	}
+
+	error = devm_request_threaded_irq(&client->dev, client->irq,
+					  NULL, tm2_touchkey_irq_handler,
+					  IRQF_ONESHOT,
+					  TM2_TOUCHKEY_DEV_NAME, touchkey);
+	if (error) {
+		dev_err(&client->dev,
+			"failed to request threaded irq: %d\n", error);
+		return error;
+	}
+
+	/* led device */
+	touchkey->led_dev.name = TM2_TOUCHKEY_DEV_NAME;
+	touchkey->led_dev.brightness = LED_ON;
+	touchkey->led_dev.max_brightness = LED_ON;
+	touchkey->led_dev.brightness_set_blocking =
+					tm2_touchkey_led_brightness_set;
+
+	error = devm_led_classdev_register(&client->dev, &touchkey->led_dev);
+	if (error) {
+		dev_err(&client->dev,
+			"failed to register touchkey led: %d\n", error);
+		return error;
+	}
+
+	if (touchkey->variant->fixed_regulator)
+		tm2_touchkey_led_brightness_set(&touchkey->led_dev, LED_ON);
+
+	return 0;
+}
+
+static int tm2_touchkey_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct tm2_touchkey_data *touchkey = i2c_get_clientdata(client);
+
+	disable_irq(client->irq);
+	tm2_touchkey_power_disable(touchkey);
+
+	return 0;
+}
+
+static int tm2_touchkey_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct tm2_touchkey_data *touchkey = i2c_get_clientdata(client);
+	int ret;
+
+	enable_irq(client->irq);
+
+	ret = tm2_touchkey_power_enable(touchkey);
+	if (ret)
+		dev_err(dev, "failed to enable power: %d\n", ret);
+
+	return ret;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(tm2_touchkey_pm_ops,
+				tm2_touchkey_suspend, tm2_touchkey_resume);
+
+static const struct i2c_device_id tm2_touchkey_id_table[] = {
+	{ .name = TM2_TOUCHKEY_DEV_NAME },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, tm2_touchkey_id_table);
+
+static const struct of_device_id tm2_touchkey_of_match[] = {
+	{
+		.compatible = "cypress,tm2-touchkey",
+		.data = &tm2_touchkey_variant,
+	}, {
+		.compatible = "cypress,midas-touchkey",
+		.data = &midas_touchkey_variant,
+	}, {
+		.compatible = "cypress,aries-touchkey",
+		.data = &aries_touchkey_variant,
+	}, {
+		.compatible = "coreriver,tc360-touchkey",
+		.data = &tc360_touchkey_variant,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tm2_touchkey_of_match);
+
+static struct i2c_driver tm2_touchkey_driver = {
+	.driver = {
+		.name = TM2_TOUCHKEY_DEV_NAME,
+		.pm = pm_sleep_ptr(&tm2_touchkey_pm_ops),
+		.of_match_table = tm2_touchkey_of_match,
+	},
+	.probe = tm2_touchkey_probe,
+	.id_table = tm2_touchkey_id_table,
+};
+module_i2c_driver(tm2_touchkey_driver);
+
+MODULE_AUTHOR("Beomho Seo <beomho.seo@samsung.com>");
+MODULE_AUTHOR("Jaechul Lee <jcsing.lee@samsung.com>");
+MODULE_DESCRIPTION("Samsung touchkey driver");
+MODULE_LICENSE("GPL v2");