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, 381 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ektf2127.c b/drivers/input/touchscreen/ektf2127.c
new file mode 100644
index 000000000..572a37d4e
--- /dev/null
+++ b/drivers/input/touchscreen/ektf2127.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for ELAN eKTF2127 i2c touchscreen controller
+ *
+ * For this driver the layout of the Chipone icn8318 i2c
+ * touchscreencontroller is used.
+ *
+ * Author:
+ * Michel Verlaan <michel.verl@gmail.com>
+ * Siebren Vroegindeweij <siebren.vroegindeweij@hotmail.com>
+ *
+ * Original chipone_icn8318 driver:
+ * Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/bits.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+
+/* Packet header defines (first byte of data send / received) */
+#define EKTF2127_NOISE			0x40
+#define EKTF2127_RESPONSE		0x52
+#define EKTF2127_REQUEST		0x53
+#define EKTF2127_HELLO			0x55
+#define EKTF2127_REPORT2		0x5a
+#define EKTF2127_REPORT			0x5d
+#define EKTF2127_CALIB_DONE		0x66
+
+/* Register defines (second byte of data send / received) */
+#define EKTF2127_ENV_NOISY		0x41
+#define EKTF2127_HEIGHT			0x60
+#define EKTF2127_WIDTH			0x63
+
+/* 2 bytes header + 5 * 3 bytes coordinates + 3 bytes pressure info + footer */
+#define EKTF2127_TOUCH_REPORT_SIZE	21
+#define EKTF2127_MAX_TOUCHES		5
+
+struct ektf2127_ts {
+	struct i2c_client *client;
+	struct input_dev *input;
+	struct gpio_desc *power_gpios;
+	struct touchscreen_properties prop;
+	int status_shift;
+};
+
+struct ektf2127_i2c_chip_data {
+	int status_shift;
+};
+
+static void ektf2127_parse_coordinates(const u8 *buf, unsigned int touch_count,
+				       struct input_mt_pos *touches)
+{
+	int index = 0;
+	int i;
+
+	for (i = 0; i < touch_count; i++) {
+		index = 2 + i * 3;
+
+		touches[i].x = (buf[index] & 0x0f);
+		touches[i].x <<= 8;
+		touches[i].x |= buf[index + 2];
+
+		touches[i].y = (buf[index] & 0xf0);
+		touches[i].y <<= 4;
+		touches[i].y |= buf[index + 1];
+	}
+}
+
+static void ektf2127_report_event(struct ektf2127_ts *ts, const u8 *buf)
+{
+	struct input_mt_pos touches[EKTF2127_MAX_TOUCHES];
+	int slots[EKTF2127_MAX_TOUCHES];
+	unsigned int touch_count, i;
+
+	touch_count = buf[1] & 0x07;
+	if (touch_count > EKTF2127_MAX_TOUCHES) {
+		dev_err(&ts->client->dev,
+			"Too many touches %d > %d\n",
+			touch_count, EKTF2127_MAX_TOUCHES);
+		touch_count = EKTF2127_MAX_TOUCHES;
+	}
+
+	ektf2127_parse_coordinates(buf, touch_count, touches);
+	input_mt_assign_slots(ts->input, slots, touches,
+			      touch_count, 0);
+
+	for (i = 0; i < touch_count; i++) {
+		input_mt_slot(ts->input, slots[i]);
+		input_mt_report_slot_state(ts->input, MT_TOOL_FINGER, true);
+		touchscreen_report_pos(ts->input, &ts->prop,
+				       touches[i].x, touches[i].y, true);
+	}
+
+	input_mt_sync_frame(ts->input);
+	input_sync(ts->input);
+}
+
+static void ektf2127_report2_contact(struct ektf2127_ts *ts, int slot,
+				     const u8 *buf, bool active)
+{
+	input_mt_slot(ts->input, slot);
+	input_mt_report_slot_state(ts->input, MT_TOOL_FINGER, active);
+
+	if (active) {
+		int x = (buf[0] & 0xf0) << 4 | buf[1];
+		int y = (buf[0] & 0x0f) << 8 | buf[2];
+
+		touchscreen_report_pos(ts->input, &ts->prop, x, y, true);
+	}
+}
+
+static void ektf2127_report2_event(struct ektf2127_ts *ts, const u8 *buf)
+{
+	ektf2127_report2_contact(ts, 0, &buf[1], !!(buf[7] & BIT(ts->status_shift)));
+	ektf2127_report2_contact(ts, 1, &buf[4], !!(buf[7] & BIT(ts->status_shift + 1)));
+
+	input_mt_sync_frame(ts->input);
+	input_sync(ts->input);
+}
+
+static irqreturn_t ektf2127_irq(int irq, void *dev_id)
+{
+	struct ektf2127_ts *ts = dev_id;
+	struct device *dev = &ts->client->dev;
+	char buf[EKTF2127_TOUCH_REPORT_SIZE];
+	int ret;
+
+	ret = i2c_master_recv(ts->client, buf, EKTF2127_TOUCH_REPORT_SIZE);
+	if (ret != EKTF2127_TOUCH_REPORT_SIZE) {
+		dev_err(dev, "Error reading touch data: %d\n", ret);
+		goto out;
+	}
+
+	switch (buf[0]) {
+	case EKTF2127_REPORT:
+		ektf2127_report_event(ts, buf);
+		break;
+
+	case EKTF2127_REPORT2:
+		ektf2127_report2_event(ts, buf);
+		break;
+
+	case EKTF2127_NOISE:
+		if (buf[1] == EKTF2127_ENV_NOISY)
+			dev_dbg(dev, "Environment is electrically noisy\n");
+		break;
+
+	case EKTF2127_HELLO:
+	case EKTF2127_CALIB_DONE:
+		break;
+
+	default:
+		dev_err(dev, "Unexpected packet header byte %#02x\n", buf[0]);
+		break;
+	}
+
+out:
+	return IRQ_HANDLED;
+}
+
+static int ektf2127_start(struct input_dev *dev)
+{
+	struct ektf2127_ts *ts = input_get_drvdata(dev);
+
+	enable_irq(ts->client->irq);
+	gpiod_set_value_cansleep(ts->power_gpios, 1);
+
+	return 0;
+}
+
+static void ektf2127_stop(struct input_dev *dev)
+{
+	struct ektf2127_ts *ts = input_get_drvdata(dev);
+
+	disable_irq(ts->client->irq);
+	gpiod_set_value_cansleep(ts->power_gpios, 0);
+}
+
+static int ektf2127_suspend(struct device *dev)
+{
+	struct ektf2127_ts *ts = i2c_get_clientdata(to_i2c_client(dev));
+
+	guard(mutex)(&ts->input->mutex);
+
+	if (input_device_enabled(ts->input))
+		ektf2127_stop(ts->input);
+
+	return 0;
+}
+
+static int ektf2127_resume(struct device *dev)
+{
+	struct ektf2127_ts *ts = i2c_get_clientdata(to_i2c_client(dev));
+
+	guard(mutex)(&ts->input->mutex);
+
+	if (input_device_enabled(ts->input))
+		ektf2127_start(ts->input);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(ektf2127_pm_ops, ektf2127_suspend,
+				ektf2127_resume);
+
+static int ektf2127_query_dimension(struct i2c_client *client, bool width)
+{
+	struct device *dev = &client->dev;
+	const char *what = width ? "width" : "height";
+	u8 what_code = width ? EKTF2127_WIDTH : EKTF2127_HEIGHT;
+	u8 buf[4];
+	int ret;
+	int error;
+
+	/* Request dimension */
+	buf[0] = EKTF2127_REQUEST;
+	buf[1] = width ? EKTF2127_WIDTH : EKTF2127_HEIGHT;
+	buf[2] = 0x00;
+	buf[3] = 0x00;
+	ret = i2c_master_send(client, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(dev, "Failed to request %s: %d\n", what, error);
+		return error;
+	}
+
+	msleep(20);
+
+	/* Read response */
+	ret = i2c_master_recv(client, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(dev, "Failed to receive %s data: %d\n", what, error);
+		return error;
+	}
+
+	if (buf[0] != EKTF2127_RESPONSE || buf[1] != what_code) {
+		dev_err(dev, "Unexpected %s data: %#02x %#02x\n",
+			what, buf[0], buf[1]);
+		return -EIO;
+	}
+
+	return (((buf[3] & 0xf0) << 4) | buf[2]) - 1;
+}
+
+static int ektf2127_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	const struct ektf2127_i2c_chip_data *chip_data;
+	struct ektf2127_ts *ts;
+	struct input_dev *input;
+	u8 buf[4];
+	int max_x, max_y;
+	int error;
+
+	if (!client->irq) {
+		dev_err(dev, "Error no irq specified\n");
+		return -EINVAL;
+	}
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	/* This requests the gpio *and* turns on the touchscreen controller */
+	ts->power_gpios = devm_gpiod_get(dev, "power", GPIOD_OUT_HIGH);
+	if (IS_ERR(ts->power_gpios))
+		return dev_err_probe(dev, PTR_ERR(ts->power_gpios), "Error getting power gpio\n");
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = client->name;
+	input->id.bustype = BUS_I2C;
+	input->open = ektf2127_start;
+	input->close = ektf2127_stop;
+
+	ts->client = client;
+
+	/* Read hello (ignore result, depends on initial power state) */
+	msleep(20);
+	i2c_master_recv(ts->client, buf, sizeof(buf));
+
+	/* Read resolution from chip */
+	max_x = ektf2127_query_dimension(client, true);
+	if (max_x < 0)
+		return max_x;
+
+	max_y = ektf2127_query_dimension(client, false);
+	if (max_y < 0)
+		return max_y;
+
+	input_set_abs_params(input, ABS_MT_POSITION_X, 0, max_x, 0, 0);
+	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, max_y, 0, 0);
+	touchscreen_parse_properties(input, true, &ts->prop);
+
+	error = input_mt_init_slots(input, EKTF2127_MAX_TOUCHES,
+				    INPUT_MT_DIRECT |
+					INPUT_MT_DROP_UNUSED |
+					INPUT_MT_TRACK);
+	if (error)
+		return error;
+
+	ts->input = input;
+
+	chip_data = i2c_get_match_data(client);
+	if (!chip_data)
+		return dev_err_probe(&client->dev, -EINVAL, "missing chip data\n");
+
+	ts->status_shift = chip_data->status_shift;
+
+	input_set_drvdata(input, ts);
+
+	error = devm_request_threaded_irq(dev, client->irq,
+					  NULL, ektf2127_irq,
+					  IRQF_ONESHOT, client->name, ts);
+	if (error) {
+		dev_err(dev, "Error requesting irq: %d\n", error);
+		return error;
+	}
+
+	/* Stop device till opened */
+	ektf2127_stop(ts->input);
+
+	error = input_register_device(input);
+	if (error)
+		return error;
+
+	i2c_set_clientdata(client, ts);
+
+	return 0;
+}
+
+static const struct ektf2127_i2c_chip_data ektf2127_data = {
+	.status_shift = 1,
+};
+
+static const struct ektf2127_i2c_chip_data ektf2232_data = {
+	.status_shift = 0,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id ektf2127_of_match[] = {
+	{ .compatible = "elan,ektf2127", .data = &ektf2127_data},
+	{ .compatible = "elan,ektf2132", .data = &ektf2127_data},
+	{ .compatible = "elan,ektf2232", .data = &ektf2232_data},
+	{}
+};
+MODULE_DEVICE_TABLE(of, ektf2127_of_match);
+#endif
+
+static const struct i2c_device_id ektf2127_i2c_id[] = {
+	{ .name = "ektf2127", .driver_data = (long)&ektf2127_data },
+	{ .name = "ektf2132", .driver_data = (long)&ektf2127_data },
+	{ .name = "ektf2232", .driver_data = (long)&ektf2232_data },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ektf2127_i2c_id);
+
+static struct i2c_driver ektf2127_driver = {
+	.driver = {
+		.name	= "elan_ektf2127",
+		.pm	= pm_sleep_ptr(&ektf2127_pm_ops),
+		.of_match_table = of_match_ptr(ektf2127_of_match),
+	},
+	.probe = ektf2127_probe,
+	.id_table = ektf2127_i2c_id,
+};
+module_i2c_driver(ektf2127_driver);
+
+MODULE_DESCRIPTION("ELAN eKTF2127/eKTF2132 I2C Touchscreen Driver");
+MODULE_AUTHOR("Michel Verlaan, Siebren Vroegindeweij");
+MODULE_LICENSE("GPL");