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, 390 insertions, 0 deletions

diff --git a/drivers/extcon/extcon-fsa9480.c b/drivers/extcon/extcon-fsa9480.c
new file mode 100644
index 000000000..a031eb091
--- /dev/null
+++ b/drivers/extcon/extcon-fsa9480.c
@@ -0,0 +1,390 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * extcon-fsa9480.c - Fairchild Semiconductor FSA9480 extcon driver
+ *
+ * Copyright (c) 2019 Tomasz Figa <tomasz.figa@gmail.com>
+ *
+ * Loosely based on old fsa9480 misc-device driver.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/interrupt.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/kobject.h>
+#include <linux/extcon-provider.h>
+#include <linux/irqdomain.h>
+#include <linux/regmap.h>
+
+/* FSA9480 I2C registers */
+#define FSA9480_REG_DEVID               0x01
+#define FSA9480_REG_CTRL                0x02
+#define FSA9480_REG_INT1                0x03
+#define FSA9480_REG_INT2                0x04
+#define FSA9480_REG_INT1_MASK           0x05
+#define FSA9480_REG_INT2_MASK           0x06
+#define FSA9480_REG_ADC                 0x07
+#define FSA9480_REG_TIMING1             0x08
+#define FSA9480_REG_TIMING2             0x09
+#define FSA9480_REG_DEV_T1              0x0a
+#define FSA9480_REG_DEV_T2              0x0b
+#define FSA9480_REG_BTN1                0x0c
+#define FSA9480_REG_BTN2                0x0d
+#define FSA9480_REG_CK                  0x0e
+#define FSA9480_REG_CK_INT1             0x0f
+#define FSA9480_REG_CK_INT2             0x10
+#define FSA9480_REG_CK_INTMASK1         0x11
+#define FSA9480_REG_CK_INTMASK2         0x12
+#define FSA9480_REG_MANSW1              0x13
+#define FSA9480_REG_MANSW2              0x14
+#define FSA9480_REG_END                 0x15
+
+/* Control */
+#define CON_SWITCH_OPEN         (1 << 4)
+#define CON_RAW_DATA            (1 << 3)
+#define CON_MANUAL_SW           (1 << 2)
+#define CON_WAIT                (1 << 1)
+#define CON_INT_MASK            (1 << 0)
+#define CON_MASK                (CON_SWITCH_OPEN | CON_RAW_DATA | \
+				 CON_MANUAL_SW | CON_WAIT)
+
+/* Device Type 1 */
+#define DEV_USB_OTG             7
+#define DEV_DEDICATED_CHG       6
+#define DEV_USB_CHG             5
+#define DEV_CAR_KIT             4
+#define DEV_UART                3
+#define DEV_USB                 2
+#define DEV_AUDIO_2             1
+#define DEV_AUDIO_1             0
+
+#define DEV_T1_USB_MASK         (DEV_USB_OTG | DEV_USB)
+#define DEV_T1_UART_MASK        (DEV_UART)
+#define DEV_T1_CHARGER_MASK     (DEV_DEDICATED_CHG | DEV_USB_CHG)
+
+/* Device Type 2 */
+#define DEV_AV                  14
+#define DEV_TTY                 13
+#define DEV_PPD                 12
+#define DEV_JIG_UART_OFF        11
+#define DEV_JIG_UART_ON         10
+#define DEV_JIG_USB_OFF         9
+#define DEV_JIG_USB_ON          8
+
+#define DEV_T2_USB_MASK         (DEV_JIG_USB_OFF | DEV_JIG_USB_ON)
+#define DEV_T2_UART_MASK        (DEV_JIG_UART_OFF | DEV_JIG_UART_ON)
+#define DEV_T2_JIG_MASK         (DEV_JIG_USB_OFF | DEV_JIG_USB_ON | \
+				 DEV_JIG_UART_OFF | DEV_JIG_UART_ON)
+
+/*
+ * Manual Switch
+ * D- [7:5] / D+ [4:2]
+ * 000: Open all / 001: USB / 010: AUDIO / 011: UART / 100: V_AUDIO
+ */
+#define SW_VAUDIO               ((4 << 5) | (4 << 2))
+#define SW_UART                 ((3 << 5) | (3 << 2))
+#define SW_AUDIO                ((2 << 5) | (2 << 2))
+#define SW_DHOST                ((1 << 5) | (1 << 2))
+#define SW_AUTO                 ((0 << 5) | (0 << 2))
+
+/* Interrupt 1 */
+#define INT1_MASK               (0xff << 0)
+#define INT_DETACH              (1 << 1)
+#define INT_ATTACH              (1 << 0)
+
+/* Interrupt 2 mask */
+#define INT2_MASK               (0x1f << 0)
+
+/* Timing Set 1 */
+#define TIMING1_ADC_500MS       (0x6 << 0)
+
+struct fsa9480_usbsw {
+	struct device *dev;
+	struct regmap *regmap;
+	struct extcon_dev *edev;
+	u16 cable;
+};
+
+static const unsigned int fsa9480_extcon_cable[] = {
+	EXTCON_USB_HOST,
+	EXTCON_USB,
+	EXTCON_CHG_USB_DCP,
+	EXTCON_CHG_USB_SDP,
+	EXTCON_CHG_USB_ACA,
+	EXTCON_JACK_LINE_OUT,
+	EXTCON_JACK_VIDEO_OUT,
+	EXTCON_JIG,
+
+	EXTCON_NONE,
+};
+
+static const u64 cable_types[] = {
+	[DEV_USB_OTG] = BIT_ULL(EXTCON_USB_HOST),
+	[DEV_DEDICATED_CHG] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_CHG_USB_DCP),
+	[DEV_USB_CHG] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_CHG_USB_SDP),
+	[DEV_CAR_KIT] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_CHG_USB_SDP)
+			| BIT_ULL(EXTCON_JACK_LINE_OUT),
+	[DEV_UART] = BIT_ULL(EXTCON_JIG),
+	[DEV_USB] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_CHG_USB_SDP),
+	[DEV_AUDIO_2] = BIT_ULL(EXTCON_JACK_LINE_OUT),
+	[DEV_AUDIO_1] = BIT_ULL(EXTCON_JACK_LINE_OUT),
+	[DEV_AV] = BIT_ULL(EXTCON_JACK_LINE_OUT)
+		   | BIT_ULL(EXTCON_JACK_VIDEO_OUT),
+	[DEV_TTY] = BIT_ULL(EXTCON_JIG),
+	[DEV_PPD] = BIT_ULL(EXTCON_JACK_LINE_OUT) | BIT_ULL(EXTCON_CHG_USB_ACA),
+	[DEV_JIG_UART_OFF] = BIT_ULL(EXTCON_JIG),
+	[DEV_JIG_UART_ON] = BIT_ULL(EXTCON_JIG),
+	[DEV_JIG_USB_OFF] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_JIG),
+	[DEV_JIG_USB_ON] = BIT_ULL(EXTCON_USB) | BIT_ULL(EXTCON_JIG),
+};
+
+/* Define regmap configuration of FSA9480 for I2C communication  */
+static bool fsa9480_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case FSA9480_REG_INT1_MASK:
+		return true;
+	default:
+		break;
+	}
+	return false;
+}
+
+static const struct regmap_config fsa9480_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.volatile_reg	= fsa9480_volatile_reg,
+	.max_register	= FSA9480_REG_END,
+};
+
+static int fsa9480_write_reg(struct fsa9480_usbsw *usbsw, int reg, int value)
+{
+	int ret;
+
+	ret = regmap_write(usbsw->regmap, reg, value);
+	if (ret < 0)
+		dev_err(usbsw->dev, "%s: err %d\n", __func__, ret);
+
+	return ret;
+}
+
+static int fsa9480_read_reg(struct fsa9480_usbsw *usbsw, int reg)
+{
+	int ret, val;
+
+	ret = regmap_read(usbsw->regmap, reg, &val);
+	if (ret < 0) {
+		dev_err(usbsw->dev, "%s: err %d\n", __func__, ret);
+		return ret;
+	}
+
+	return val;
+}
+
+static int fsa9480_read_irq(struct fsa9480_usbsw *usbsw, int *value)
+{
+	u8 regs[2];
+	int ret;
+
+	ret = regmap_bulk_read(usbsw->regmap, FSA9480_REG_INT1, regs, 2);
+	if (ret < 0)
+		dev_err(usbsw->dev, "%s: err %d\n", __func__, ret);
+
+	*value = regs[1] << 8 | regs[0];
+	return ret;
+}
+
+static void fsa9480_handle_change(struct fsa9480_usbsw *usbsw,
+				  u16 mask, bool attached)
+{
+	while (mask) {
+		int dev = fls64(mask) - 1;
+		u64 cables = cable_types[dev];
+
+		while (cables) {
+			int cable = fls64(cables) - 1;
+
+			extcon_set_state_sync(usbsw->edev, cable, attached);
+			cables &= ~BIT_ULL(cable);
+		}
+
+		mask &= ~BIT_ULL(dev);
+	}
+}
+
+static void fsa9480_detect_dev(struct fsa9480_usbsw *usbsw)
+{
+	int val1, val2;
+	u16 val;
+
+	val1 = fsa9480_read_reg(usbsw, FSA9480_REG_DEV_T1);
+	val2 = fsa9480_read_reg(usbsw, FSA9480_REG_DEV_T2);
+	if (val1 < 0 || val2 < 0) {
+		dev_err(usbsw->dev, "%s: failed to read registers", __func__);
+		return;
+	}
+	val = val2 << 8 | val1;
+
+	dev_info(usbsw->dev, "dev1: 0x%x, dev2: 0x%x\n", val1, val2);
+
+	/* handle detached cables first */
+	fsa9480_handle_change(usbsw, usbsw->cable & ~val, false);
+
+	/* then handle attached ones */
+	fsa9480_handle_change(usbsw, val & ~usbsw->cable, true);
+
+	usbsw->cable = val;
+}
+
+static irqreturn_t fsa9480_irq_handler(int irq, void *data)
+{
+	struct fsa9480_usbsw *usbsw = data;
+	int intr = 0;
+
+	/* clear interrupt */
+	fsa9480_read_irq(usbsw, &intr);
+	if (!intr)
+		return IRQ_NONE;
+
+	/* device detection */
+	fsa9480_detect_dev(usbsw);
+
+	return IRQ_HANDLED;
+}
+
+static int fsa9480_probe(struct i2c_client *client)
+{
+	struct fsa9480_usbsw *info;
+	int ret;
+
+	if (!client->irq) {
+		dev_err(&client->dev, "no interrupt provided\n");
+		return -EINVAL;
+	}
+
+	info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+	info->dev = &client->dev;
+
+	i2c_set_clientdata(client, info);
+
+	/* External connector */
+	info->edev = devm_extcon_dev_allocate(info->dev,
+					      fsa9480_extcon_cable);
+	if (IS_ERR(info->edev)) {
+		dev_err(info->dev, "failed to allocate memory for extcon\n");
+		ret = -ENOMEM;
+		return ret;
+	}
+
+	ret = devm_extcon_dev_register(info->dev, info->edev);
+	if (ret) {
+		dev_err(info->dev, "failed to register extcon device\n");
+		return ret;
+	}
+
+	info->regmap = devm_regmap_init_i2c(client, &fsa9480_regmap_config);
+	if (IS_ERR(info->regmap)) {
+		ret = PTR_ERR(info->regmap);
+		dev_err(info->dev, "failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	/* ADC Detect Time: 500ms */
+	fsa9480_write_reg(info, FSA9480_REG_TIMING1, TIMING1_ADC_500MS);
+
+	/* configure automatic switching */
+	fsa9480_write_reg(info, FSA9480_REG_CTRL, CON_MASK);
+
+	/* unmask interrupt (attach/detach only) */
+	fsa9480_write_reg(info, FSA9480_REG_INT1_MASK,
+			  INT1_MASK & ~(INT_ATTACH | INT_DETACH));
+	fsa9480_write_reg(info, FSA9480_REG_INT2_MASK, INT2_MASK);
+
+	ret = devm_request_threaded_irq(info->dev, client->irq, NULL,
+					fsa9480_irq_handler,
+					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+					"fsa9480", info);
+	if (ret) {
+		dev_err(info->dev, "failed to request IRQ\n");
+		return ret;
+	}
+
+	devm_device_init_wakeup(info->dev);
+	fsa9480_detect_dev(info);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int fsa9480_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	if (device_may_wakeup(&client->dev) && client->irq)
+		enable_irq_wake(client->irq);
+
+	return 0;
+}
+
+static int fsa9480_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	if (device_may_wakeup(&client->dev) && client->irq)
+		disable_irq_wake(client->irq);
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops fsa9480_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(fsa9480_suspend, fsa9480_resume)
+};
+
+static const struct i2c_device_id fsa9480_id[] = {
+	{ "fsa9480" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, fsa9480_id);
+
+static const struct of_device_id fsa9480_of_match[] = {
+	{ .compatible = "fcs,fsa9480", },
+	{ .compatible = "fcs,fsa880", },
+	{ .compatible = "ti,tsu6111", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, fsa9480_of_match);
+
+static struct i2c_driver fsa9480_i2c_driver = {
+	.driver			= {
+		.name		= "fsa9480",
+		.pm		= &fsa9480_pm_ops,
+		.of_match_table = fsa9480_of_match,
+	},
+	.probe			= fsa9480_probe,
+	.id_table		= fsa9480_id,
+};
+
+static int __init fsa9480_module_init(void)
+{
+	return i2c_add_driver(&fsa9480_i2c_driver);
+}
+subsys_initcall(fsa9480_module_init);
+
+static void __exit fsa9480_module_exit(void)
+{
+	i2c_del_driver(&fsa9480_i2c_driver);
+}
+module_exit(fsa9480_module_exit);
+
+MODULE_DESCRIPTION("Fairchild Semiconductor FSA9480 extcon driver");
+MODULE_AUTHOR("Tomasz Figa <tomasz.figa@gmail.com>");
+MODULE_LICENSE("GPL");