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, 473 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/sx8654.c b/drivers/input/touchscreen/sx8654.c
new file mode 100644
index 000000000..0d92aaeea
--- /dev/null
+++ b/drivers/input/touchscreen/sx8654.c
@@ -0,0 +1,473 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Semtech SX8654 I2C touchscreen controller.
+ *
+ * Copyright (c) 2015 Armadeus Systems
+ *	Sébastien Szymanski <sebastien.szymanski@armadeus.com>
+ *
+ * Using code from:
+ *  - sx865x.c
+ *	Copyright (c) 2013 U-MoBo Srl
+ *	Pierluigi Passaro <p.passaro@u-mobo.com>
+ *  - sx8650.c
+ *      Copyright (c) 2009 Wayne Roberts
+ *  - tsc2007.c
+ *      Copyright (c) 2008 Kwangwoo Lee
+ *  - ads7846.c
+ *      Copyright (c) 2005 David Brownell
+ *      Copyright (c) 2006 Nokia Corporation
+ *  - corgi_ts.c
+ *      Copyright (C) 2004-2005 Richard Purdie
+ *  - omap_ts.[hc], ads7846.h, ts_osk.c
+ *      Copyright (C) 2002 MontaVista Software
+ *      Copyright (C) 2004 Texas Instruments
+ *      Copyright (C) 2005 Dirk Behme
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/touchscreen.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+/* register addresses */
+#define I2C_REG_TOUCH0			0x00
+#define I2C_REG_TOUCH1			0x01
+#define I2C_REG_CHANMASK		0x04
+#define I2C_REG_IRQMASK			0x22
+#define I2C_REG_IRQSRC			0x23
+#define I2C_REG_SOFTRESET		0x3f
+
+#define I2C_REG_SX8650_STAT		0x05
+#define SX8650_STAT_CONVIRQ		BIT(7)
+
+/* commands */
+#define CMD_READ_REGISTER		0x40
+#define CMD_PENTRG			0xe0
+
+/* value for I2C_REG_SOFTRESET */
+#define SOFTRESET_VALUE			0xde
+
+/* bits for I2C_REG_IRQSRC */
+#define IRQ_PENTOUCH_TOUCHCONVDONE	BIT(3)
+#define IRQ_PENRELEASE			BIT(2)
+
+/* bits for RegTouch1 */
+#define CONDIRQ				0x20
+#define RPDNT_100K			0x00
+#define FILT_7SA			0x03
+
+/* bits for I2C_REG_CHANMASK */
+#define CONV_X				BIT(7)
+#define CONV_Y				BIT(6)
+
+/* coordinates rate: higher nibble of CTRL0 register */
+#define RATE_MANUAL			0x00
+#define RATE_5000CPS			0xf0
+
+/* power delay: lower nibble of CTRL0 register */
+#define POWDLY_1_1MS			0x0b
+
+/* for sx8650, as we have no pen release IRQ there: timeout in ns following the
+ * last PENIRQ after which we assume the pen is lifted.
+ */
+#define SX8650_PENIRQ_TIMEOUT		msecs_to_jiffies(10)
+
+#define MAX_12BIT			((1 << 12) - 1)
+#define MAX_I2C_READ_LEN		10 /* see datasheet section 5.1.5 */
+
+/* channel definition */
+#define CH_X				0x00
+#define CH_Y				0x01
+
+struct sx865x_data {
+	u8 cmd_manual;
+	u8 chan_mask;
+	bool has_irq_penrelease;
+	bool has_reg_irqmask;
+	irq_handler_t irqh;
+};
+
+struct sx8654 {
+	struct input_dev *input;
+	struct i2c_client *client;
+	struct gpio_desc *gpio_reset;
+
+	spinlock_t lock;	/* for input reporting from irq/timer */
+	struct timer_list timer;
+
+	struct touchscreen_properties props;
+
+	const struct sx865x_data *data;
+};
+
+static inline void sx865x_penrelease(struct sx8654 *ts)
+{
+	struct input_dev *input_dev = ts->input;
+
+	input_report_key(input_dev, BTN_TOUCH, 0);
+	input_sync(input_dev);
+}
+
+static void sx865x_penrelease_timer_handler(struct timer_list *t)
+{
+	struct sx8654 *ts = timer_container_of(ts, t, timer);
+
+	dev_dbg(&ts->client->dev, "penrelease by timer\n");
+
+	guard(spinlock_irqsave)(&ts->lock);
+	sx865x_penrelease(ts);
+}
+
+static irqreturn_t sx8650_irq(int irq, void *handle)
+{
+	struct sx8654 *ts = handle;
+	struct device *dev = &ts->client->dev;
+	int len, i;
+	u8 stat;
+	u16 x, y;
+	u16 ch;
+	u16 chdata;
+	__be16 data[MAX_I2C_READ_LEN / sizeof(__be16)];
+	u8 nchan = hweight32(ts->data->chan_mask);
+	u8 readlen = nchan * sizeof(*data);
+
+	stat = i2c_smbus_read_byte_data(ts->client, CMD_READ_REGISTER
+						    | I2C_REG_SX8650_STAT);
+
+	if (!(stat & SX8650_STAT_CONVIRQ)) {
+		dev_dbg(dev, "%s ignore stat [0x%02x]", __func__, stat);
+		return IRQ_HANDLED;
+	}
+
+	len = i2c_master_recv(ts->client, (u8 *)data, readlen);
+	if (len != readlen) {
+		dev_dbg(dev, "ignore short recv (%d)\n", len);
+		return IRQ_HANDLED;
+	}
+
+	guard(spinlock_irqsave)(&ts->lock);
+
+	x = 0;
+	y = 0;
+	for (i = 0; i < nchan; i++) {
+		chdata = be16_to_cpu(data[i]);
+
+		if (unlikely(chdata == 0xFFFF)) {
+			dev_dbg(dev, "invalid qualified data @ %d\n", i);
+			continue;
+		} else if (unlikely(chdata & 0x8000)) {
+			dev_warn(dev, "hibit @ %d [0x%04x]\n", i, chdata);
+			continue;
+		}
+
+		ch = chdata >> 12;
+		if (ch == CH_X)
+			x = chdata & MAX_12BIT;
+		else if (ch == CH_Y)
+			y = chdata & MAX_12BIT;
+		else
+			dev_warn(dev, "unknown channel %d [0x%04x]\n", ch,
+				 chdata);
+	}
+
+	touchscreen_report_pos(ts->input, &ts->props, x, y, false);
+	input_report_key(ts->input, BTN_TOUCH, 1);
+	input_sync(ts->input);
+	dev_dbg(dev, "point(%4d,%4d)\n", x, y);
+
+	mod_timer(&ts->timer, jiffies + SX8650_PENIRQ_TIMEOUT);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sx8654_irq(int irq, void *handle)
+{
+	struct sx8654 *sx8654 = handle;
+	int irqsrc;
+	u8 data[4];
+	unsigned int x, y;
+	int retval;
+
+	irqsrc = i2c_smbus_read_byte_data(sx8654->client,
+					  CMD_READ_REGISTER | I2C_REG_IRQSRC);
+	dev_dbg(&sx8654->client->dev, "irqsrc = 0x%x", irqsrc);
+
+	if (irqsrc < 0)
+		goto out;
+
+	if (irqsrc & IRQ_PENRELEASE) {
+		dev_dbg(&sx8654->client->dev, "pen release interrupt");
+
+		input_report_key(sx8654->input, BTN_TOUCH, 0);
+		input_sync(sx8654->input);
+	}
+
+	if (irqsrc & IRQ_PENTOUCH_TOUCHCONVDONE) {
+		dev_dbg(&sx8654->client->dev, "pen touch interrupt");
+
+		retval = i2c_master_recv(sx8654->client, data, sizeof(data));
+		if (retval != sizeof(data))
+			goto out;
+
+		/* invalid data */
+		if (unlikely(data[0] & 0x80 || data[2] & 0x80))
+			goto out;
+
+		x = ((data[0] & 0xf) << 8) | (data[1]);
+		y = ((data[2] & 0xf) << 8) | (data[3]);
+
+		touchscreen_report_pos(sx8654->input, &sx8654->props, x, y,
+				       false);
+		input_report_key(sx8654->input, BTN_TOUCH, 1);
+		input_sync(sx8654->input);
+
+		dev_dbg(&sx8654->client->dev, "point(%4d,%4d)\n", x, y);
+	}
+
+out:
+	return IRQ_HANDLED;
+}
+
+static int sx8654_reset(struct sx8654 *ts)
+{
+	int err;
+
+	if (ts->gpio_reset) {
+		gpiod_set_value_cansleep(ts->gpio_reset, 1);
+		udelay(2); /* Tpulse > 1µs */
+		gpiod_set_value_cansleep(ts->gpio_reset, 0);
+	} else {
+		dev_dbg(&ts->client->dev, "NRST unavailable, try softreset\n");
+		err = i2c_smbus_write_byte_data(ts->client, I2C_REG_SOFTRESET,
+						SOFTRESET_VALUE);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int sx8654_open(struct input_dev *dev)
+{
+	struct sx8654 *sx8654 = input_get_drvdata(dev);
+	struct i2c_client *client = sx8654->client;
+	int error;
+
+	/* enable pen trigger mode */
+	error = i2c_smbus_write_byte_data(client, I2C_REG_TOUCH0,
+					  RATE_5000CPS | POWDLY_1_1MS);
+	if (error) {
+		dev_err(&client->dev, "writing to I2C_REG_TOUCH0 failed");
+		return error;
+	}
+
+	error = i2c_smbus_write_byte(client, CMD_PENTRG);
+	if (error) {
+		dev_err(&client->dev, "writing command CMD_PENTRG failed");
+		return error;
+	}
+
+	enable_irq(client->irq);
+
+	return 0;
+}
+
+static void sx8654_close(struct input_dev *dev)
+{
+	struct sx8654 *sx8654 = input_get_drvdata(dev);
+	struct i2c_client *client = sx8654->client;
+	int error;
+
+	disable_irq(client->irq);
+
+	if (!sx8654->data->has_irq_penrelease)
+		timer_delete_sync(&sx8654->timer);
+
+	/* enable manual mode mode */
+	error = i2c_smbus_write_byte(client, sx8654->data->cmd_manual);
+	if (error) {
+		dev_err(&client->dev, "writing command CMD_MANUAL failed");
+		return;
+	}
+
+	error = i2c_smbus_write_byte_data(client, I2C_REG_TOUCH0, RATE_MANUAL);
+	if (error) {
+		dev_err(&client->dev, "writing to I2C_REG_TOUCH0 failed");
+		return;
+	}
+}
+
+static int sx8654_probe(struct i2c_client *client)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(client);
+	struct sx8654 *sx8654;
+	struct input_dev *input;
+	int error;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENXIO;
+
+	sx8654 = devm_kzalloc(&client->dev, sizeof(*sx8654), GFP_KERNEL);
+	if (!sx8654)
+		return -ENOMEM;
+
+	sx8654->gpio_reset = devm_gpiod_get_optional(&client->dev, "reset",
+						     GPIOD_OUT_HIGH);
+	if (IS_ERR(sx8654->gpio_reset))
+		return dev_err_probe(&client->dev, PTR_ERR(sx8654->gpio_reset),
+				     "unable to get reset-gpio\n");
+	dev_dbg(&client->dev, "got GPIO reset pin\n");
+
+	sx8654->data = device_get_match_data(&client->dev);
+	if (!sx8654->data)
+		sx8654->data = (const struct sx865x_data *)id->driver_data;
+	if (!sx8654->data) {
+		dev_err(&client->dev, "invalid or missing device data\n");
+		return -EINVAL;
+	}
+
+	if (!sx8654->data->has_irq_penrelease) {
+		dev_dbg(&client->dev, "use timer for penrelease\n");
+		timer_setup(&sx8654->timer, sx865x_penrelease_timer_handler, 0);
+		spin_lock_init(&sx8654->lock);
+	}
+
+	input = devm_input_allocate_device(&client->dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = "SX8654 I2C Touchscreen";
+	input->id.bustype = BUS_I2C;
+	input->dev.parent = &client->dev;
+	input->open = sx8654_open;
+	input->close = sx8654_close;
+
+	__set_bit(INPUT_PROP_DIRECT, input->propbit);
+	input_set_capability(input, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input, ABS_X, 0, MAX_12BIT, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, MAX_12BIT, 0, 0);
+
+	touchscreen_parse_properties(input, false, &sx8654->props);
+
+	sx8654->client = client;
+	sx8654->input = input;
+
+	input_set_drvdata(sx8654->input, sx8654);
+
+	error = sx8654_reset(sx8654);
+	if (error) {
+		dev_err(&client->dev, "reset failed");
+		return error;
+	}
+
+	error = i2c_smbus_write_byte_data(client, I2C_REG_CHANMASK,
+					  sx8654->data->chan_mask);
+	if (error) {
+		dev_err(&client->dev, "writing to I2C_REG_CHANMASK failed");
+		return error;
+	}
+
+	if (sx8654->data->has_reg_irqmask) {
+		error = i2c_smbus_write_byte_data(client, I2C_REG_IRQMASK,
+						  IRQ_PENTOUCH_TOUCHCONVDONE |
+							IRQ_PENRELEASE);
+		if (error) {
+			dev_err(&client->dev, "writing I2C_REG_IRQMASK failed");
+			return error;
+		}
+	}
+
+	error = i2c_smbus_write_byte_data(client, I2C_REG_TOUCH1,
+					  CONDIRQ | RPDNT_100K | FILT_7SA);
+	if (error) {
+		dev_err(&client->dev, "writing to I2C_REG_TOUCH1 failed");
+		return error;
+	}
+
+	/*
+	 * Start with the interrupt disabled, it will be enabled in
+	 * sx8654_open().
+	 */
+	error = devm_request_threaded_irq(&client->dev, client->irq,
+					  NULL, sx8654->data->irqh,
+					  IRQF_ONESHOT | IRQF_NO_AUTOEN,
+					  client->name, sx8654);
+	if (error) {
+		dev_err(&client->dev,
+			"Failed to enable IRQ %d, error: %d\n",
+			client->irq, error);
+		return error;
+	}
+
+	error = input_register_device(sx8654->input);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static const struct sx865x_data sx8650_data = {
+	.cmd_manual		= 0xb0,
+	.has_irq_penrelease	= false,
+	.has_reg_irqmask	= false,
+	.chan_mask		= (CONV_X | CONV_Y),
+	.irqh			= sx8650_irq,
+};
+
+static const struct sx865x_data sx8654_data = {
+	.cmd_manual		= 0xc0,
+	.has_irq_penrelease	= true,
+	.has_reg_irqmask	= true,
+	.chan_mask		= (CONV_X | CONV_Y),
+	.irqh			= sx8654_irq,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id sx8654_of_match[] = {
+	{
+		.compatible = "semtech,sx8650",
+		.data = &sx8650_data,
+	}, {
+		.compatible = "semtech,sx8654",
+		.data = &sx8654_data,
+	}, {
+		.compatible = "semtech,sx8655",
+		.data = &sx8654_data,
+	}, {
+		.compatible = "semtech,sx8656",
+		.data = &sx8654_data,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sx8654_of_match);
+#endif
+
+static const struct i2c_device_id sx8654_id_table[] = {
+	{ .name = "semtech_sx8650", .driver_data = (long)&sx8650_data },
+	{ .name = "semtech_sx8654", .driver_data = (long)&sx8654_data },
+	{ .name = "semtech_sx8655", .driver_data = (long)&sx8654_data },
+	{ .name = "semtech_sx8656", .driver_data = (long)&sx8654_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sx8654_id_table);
+
+static struct i2c_driver sx8654_driver = {
+	.driver = {
+		.name = "sx8654",
+		.of_match_table = of_match_ptr(sx8654_of_match),
+	},
+	.id_table = sx8654_id_table,
+	.probe = sx8654_probe,
+};
+module_i2c_driver(sx8654_driver);
+
+MODULE_AUTHOR("Sébastien Szymanski <sebastien.szymanski@armadeus.com>");
+MODULE_DESCRIPTION("Semtech SX8654 I2C Touchscreen Driver");
+MODULE_LICENSE("GPL");