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, 398 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/wm831x-ts.c b/drivers/input/touchscreen/wm831x-ts.c
new file mode 100644
index 000000000..98f8ec408
--- /dev/null
+++ b/drivers/input/touchscreen/wm831x-ts.c
@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Touchscreen driver for WM831x PMICs
+ *
+ * Copyright 2011 Wolfson Microelectronics plc.
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/pm.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mfd/wm831x/core.h>
+#include <linux/mfd/wm831x/irq.h>
+#include <linux/mfd/wm831x/pdata.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+/*
+ * R16424 (0x4028) - Touch Control 1
+ */
+#define WM831X_TCH_ENA                          0x8000  /* TCH_ENA */
+#define WM831X_TCH_CVT_ENA                      0x4000  /* TCH_CVT_ENA */
+#define WM831X_TCH_SLPENA                       0x1000  /* TCH_SLPENA */
+#define WM831X_TCH_Z_ENA                        0x0400  /* TCH_Z_ENA */
+#define WM831X_TCH_Y_ENA                        0x0200  /* TCH_Y_ENA */
+#define WM831X_TCH_X_ENA                        0x0100  /* TCH_X_ENA */
+#define WM831X_TCH_DELAY_MASK                   0x00E0  /* TCH_DELAY - [7:5] */
+#define WM831X_TCH_DELAY_SHIFT                       5  /* TCH_DELAY - [7:5] */
+#define WM831X_TCH_DELAY_WIDTH                       3  /* TCH_DELAY - [7:5] */
+#define WM831X_TCH_RATE_MASK                    0x001F  /* TCH_RATE - [4:0] */
+#define WM831X_TCH_RATE_SHIFT                        0  /* TCH_RATE - [4:0] */
+#define WM831X_TCH_RATE_WIDTH                        5  /* TCH_RATE - [4:0] */
+
+/*
+ * R16425 (0x4029) - Touch Control 2
+ */
+#define WM831X_TCH_PD_WK                        0x2000  /* TCH_PD_WK */
+#define WM831X_TCH_5WIRE                        0x1000  /* TCH_5WIRE */
+#define WM831X_TCH_PDONLY                       0x0800  /* TCH_PDONLY */
+#define WM831X_TCH_ISEL                         0x0100  /* TCH_ISEL */
+#define WM831X_TCH_RPU_MASK                     0x000F  /* TCH_RPU - [3:0] */
+#define WM831X_TCH_RPU_SHIFT                         0  /* TCH_RPU - [3:0] */
+#define WM831X_TCH_RPU_WIDTH                         4  /* TCH_RPU - [3:0] */
+
+/*
+ * R16426-8 (0x402A-C) - Touch Data X/Y/X
+ */
+#define WM831X_TCH_PD                           0x8000  /* TCH_PD1 */
+#define WM831X_TCH_DATA_MASK                    0x0FFF  /* TCH_DATA - [11:0] */
+#define WM831X_TCH_DATA_SHIFT                        0  /* TCH_DATA - [11:0] */
+#define WM831X_TCH_DATA_WIDTH                       12  /* TCH_DATA - [11:0] */
+
+struct wm831x_ts {
+	struct input_dev *input_dev;
+	struct wm831x *wm831x;
+	unsigned int data_irq;
+	unsigned int pd_irq;
+	bool pressure;
+	bool pen_down;
+	struct work_struct pd_data_work;
+};
+
+static void wm831x_pd_data_work(struct work_struct *work)
+{
+	struct wm831x_ts *wm831x_ts =
+		container_of(work, struct wm831x_ts, pd_data_work);
+
+	if (wm831x_ts->pen_down) {
+		enable_irq(wm831x_ts->data_irq);
+		dev_dbg(wm831x_ts->wm831x->dev, "IRQ PD->DATA done\n");
+	} else {
+		enable_irq(wm831x_ts->pd_irq);
+		dev_dbg(wm831x_ts->wm831x->dev, "IRQ DATA->PD done\n");
+	}
+}
+
+static irqreturn_t wm831x_ts_data_irq(int irq, void *irq_data)
+{
+	struct wm831x_ts *wm831x_ts = irq_data;
+	struct wm831x *wm831x = wm831x_ts->wm831x;
+	static int data_types[] = { ABS_X, ABS_Y, ABS_PRESSURE };
+	u16 data[3];
+	int count;
+	int i, ret;
+
+	if (wm831x_ts->pressure)
+		count = 3;
+	else
+		count = 2;
+
+	wm831x_set_bits(wm831x, WM831X_INTERRUPT_STATUS_1,
+			WM831X_TCHDATA_EINT, WM831X_TCHDATA_EINT);
+
+	ret = wm831x_bulk_read(wm831x, WM831X_TOUCH_DATA_X, count,
+			       data);
+	if (ret != 0) {
+		dev_err(wm831x->dev, "Failed to read touch data: %d\n",
+			ret);
+		return IRQ_NONE;
+	}
+
+	/*
+	 * We get a pen down reading on every reading, report pen up if any
+	 * individual reading does so.
+	 */
+	wm831x_ts->pen_down = true;
+	for (i = 0; i < count; i++) {
+		if (!(data[i] & WM831X_TCH_PD)) {
+			wm831x_ts->pen_down = false;
+			continue;
+		}
+		input_report_abs(wm831x_ts->input_dev, data_types[i],
+				 data[i] & WM831X_TCH_DATA_MASK);
+	}
+
+	if (!wm831x_ts->pen_down) {
+		/* Switch from data to pen down */
+		dev_dbg(wm831x->dev, "IRQ DATA->PD\n");
+
+		disable_irq_nosync(wm831x_ts->data_irq);
+
+		/* Don't need data any more */
+		wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+				WM831X_TCH_X_ENA | WM831X_TCH_Y_ENA |
+				WM831X_TCH_Z_ENA, 0);
+
+		/* Flush any final samples that arrived while reading */
+		wm831x_set_bits(wm831x, WM831X_INTERRUPT_STATUS_1,
+				WM831X_TCHDATA_EINT, WM831X_TCHDATA_EINT);
+
+		wm831x_bulk_read(wm831x, WM831X_TOUCH_DATA_X, count, data);
+
+		if (wm831x_ts->pressure)
+			input_report_abs(wm831x_ts->input_dev,
+					 ABS_PRESSURE, 0);
+
+		input_report_key(wm831x_ts->input_dev, BTN_TOUCH, 0);
+
+		schedule_work(&wm831x_ts->pd_data_work);
+	} else {
+		input_report_key(wm831x_ts->input_dev, BTN_TOUCH, 1);
+	}
+
+	input_sync(wm831x_ts->input_dev);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t wm831x_ts_pen_down_irq(int irq, void *irq_data)
+{
+	struct wm831x_ts *wm831x_ts = irq_data;
+	struct wm831x *wm831x = wm831x_ts->wm831x;
+	int ena = 0;
+
+	if (wm831x_ts->pen_down)
+		return IRQ_HANDLED;
+
+	disable_irq_nosync(wm831x_ts->pd_irq);
+
+	/* Start collecting data */
+	if (wm831x_ts->pressure)
+		ena |= WM831X_TCH_Z_ENA;
+
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+			WM831X_TCH_X_ENA | WM831X_TCH_Y_ENA | WM831X_TCH_Z_ENA,
+			WM831X_TCH_X_ENA | WM831X_TCH_Y_ENA | ena);
+
+	wm831x_set_bits(wm831x, WM831X_INTERRUPT_STATUS_1,
+			WM831X_TCHPD_EINT, WM831X_TCHPD_EINT);
+
+	wm831x_ts->pen_down = true;
+
+	/* Switch from pen down to data */
+	dev_dbg(wm831x->dev, "IRQ PD->DATA\n");
+	schedule_work(&wm831x_ts->pd_data_work);
+
+	return IRQ_HANDLED;
+}
+
+static int wm831x_ts_input_open(struct input_dev *idev)
+{
+	struct wm831x_ts *wm831x_ts = input_get_drvdata(idev);
+	struct wm831x *wm831x = wm831x_ts->wm831x;
+
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+			WM831X_TCH_ENA | WM831X_TCH_CVT_ENA |
+			WM831X_TCH_X_ENA | WM831X_TCH_Y_ENA |
+			WM831X_TCH_Z_ENA, WM831X_TCH_ENA);
+
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+			WM831X_TCH_CVT_ENA, WM831X_TCH_CVT_ENA);
+
+	return 0;
+}
+
+static void wm831x_ts_input_close(struct input_dev *idev)
+{
+	struct wm831x_ts *wm831x_ts = input_get_drvdata(idev);
+	struct wm831x *wm831x = wm831x_ts->wm831x;
+
+	/* Shut the controller down, disabling all other functionality too */
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+			WM831X_TCH_ENA | WM831X_TCH_X_ENA |
+			WM831X_TCH_Y_ENA | WM831X_TCH_Z_ENA, 0);
+
+	/* Make sure any pending IRQs are done, the above will prevent
+	 * new ones firing.
+	 */
+	synchronize_irq(wm831x_ts->data_irq);
+	synchronize_irq(wm831x_ts->pd_irq);
+
+	/* Make sure the IRQ completion work is quiesced */
+	flush_work(&wm831x_ts->pd_data_work);
+
+	/* If we ended up with the pen down then make sure we revert back
+	 * to pen detection state for the next time we start up.
+	 */
+	if (wm831x_ts->pen_down) {
+		disable_irq(wm831x_ts->data_irq);
+		enable_irq(wm831x_ts->pd_irq);
+		wm831x_ts->pen_down = false;
+	}
+}
+
+static int wm831x_ts_probe(struct platform_device *pdev)
+{
+	struct wm831x_ts *wm831x_ts;
+	struct wm831x *wm831x = dev_get_drvdata(pdev->dev.parent);
+	struct wm831x_pdata *core_pdata = dev_get_platdata(pdev->dev.parent);
+	struct wm831x_touch_pdata *pdata = NULL;
+	struct input_dev *input_dev;
+	int error, irqf;
+
+	if (core_pdata)
+		pdata = core_pdata->touch;
+
+	wm831x_ts = devm_kzalloc(&pdev->dev, sizeof(struct wm831x_ts),
+				 GFP_KERNEL);
+	input_dev = devm_input_allocate_device(&pdev->dev);
+	if (!wm831x_ts || !input_dev) {
+		error = -ENOMEM;
+		goto err_alloc;
+	}
+
+	wm831x_ts->wm831x = wm831x;
+	wm831x_ts->input_dev = input_dev;
+	INIT_WORK(&wm831x_ts->pd_data_work, wm831x_pd_data_work);
+
+	/*
+	 * If we have a direct IRQ use it, otherwise use the interrupt
+	 * from the WM831x IRQ controller.
+	 */
+	wm831x_ts->data_irq = wm831x_irq(wm831x,
+					 platform_get_irq_byname(pdev,
+								 "TCHDATA"));
+	if (pdata && pdata->data_irq)
+		wm831x_ts->data_irq = pdata->data_irq;
+
+	wm831x_ts->pd_irq = wm831x_irq(wm831x,
+				       platform_get_irq_byname(pdev, "TCHPD"));
+	if (pdata && pdata->pd_irq)
+		wm831x_ts->pd_irq = pdata->pd_irq;
+
+	if (pdata)
+		wm831x_ts->pressure = pdata->pressure;
+	else
+		wm831x_ts->pressure = true;
+
+	/* Five wire touchscreens can't report pressure */
+	if (pdata && pdata->fivewire) {
+		wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_2,
+				WM831X_TCH_5WIRE, WM831X_TCH_5WIRE);
+
+		/* Pressure measurements are not possible for five wire mode */
+		WARN_ON(pdata->pressure && pdata->fivewire);
+		wm831x_ts->pressure = false;
+	} else {
+		wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_2,
+				WM831X_TCH_5WIRE, 0);
+	}
+
+	if (pdata) {
+		switch (pdata->isel) {
+		default:
+			dev_err(&pdev->dev, "Unsupported ISEL setting: %d\n",
+				pdata->isel);
+			fallthrough;
+		case 200:
+		case 0:
+			wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_2,
+					WM831X_TCH_ISEL, 0);
+			break;
+		case 400:
+			wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_2,
+					WM831X_TCH_ISEL, WM831X_TCH_ISEL);
+			break;
+		}
+	}
+
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_2,
+			WM831X_TCH_PDONLY, 0);
+
+	/* Default to 96 samples/sec */
+	wm831x_set_bits(wm831x, WM831X_TOUCH_CONTROL_1,
+			WM831X_TCH_RATE_MASK, 6);
+
+	if (pdata && pdata->data_irqf)
+		irqf = pdata->data_irqf;
+	else
+		irqf = IRQF_TRIGGER_HIGH;
+
+	error = request_threaded_irq(wm831x_ts->data_irq,
+				     NULL, wm831x_ts_data_irq,
+				     irqf | IRQF_ONESHOT | IRQF_NO_AUTOEN,
+				     "Touchscreen data", wm831x_ts);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request data IRQ %d: %d\n",
+			wm831x_ts->data_irq, error);
+		goto err_alloc;
+	}
+
+	if (pdata && pdata->pd_irqf)
+		irqf = pdata->pd_irqf;
+	else
+		irqf = IRQF_TRIGGER_HIGH;
+
+	error = request_threaded_irq(wm831x_ts->pd_irq,
+				     NULL, wm831x_ts_pen_down_irq,
+				     irqf | IRQF_ONESHOT,
+				     "Touchscreen pen down", wm831x_ts);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request pen down IRQ %d: %d\n",
+			wm831x_ts->pd_irq, error);
+		goto err_data_irq;
+	}
+
+	/* set up touch configuration */
+	input_dev->name = "WM831x touchscreen";
+	input_dev->phys = "wm831x";
+	input_dev->open = wm831x_ts_input_open;
+	input_dev->close = wm831x_ts_input_close;
+
+	__set_bit(EV_ABS, input_dev->evbit);
+	__set_bit(EV_KEY, input_dev->evbit);
+	__set_bit(BTN_TOUCH, input_dev->keybit);
+
+	input_set_abs_params(input_dev, ABS_X, 0, 4095, 5, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, 4095, 5, 0);
+	if (wm831x_ts->pressure)
+		input_set_abs_params(input_dev, ABS_PRESSURE, 0, 4095, 5, 0);
+
+	input_set_drvdata(input_dev, wm831x_ts);
+	input_dev->dev.parent = &pdev->dev;
+
+	error = input_register_device(input_dev);
+	if (error)
+		goto err_pd_irq;
+
+	platform_set_drvdata(pdev, wm831x_ts);
+	return 0;
+
+err_pd_irq:
+	free_irq(wm831x_ts->pd_irq, wm831x_ts);
+err_data_irq:
+	free_irq(wm831x_ts->data_irq, wm831x_ts);
+err_alloc:
+
+	return error;
+}
+
+static void wm831x_ts_remove(struct platform_device *pdev)
+{
+	struct wm831x_ts *wm831x_ts = platform_get_drvdata(pdev);
+
+	free_irq(wm831x_ts->pd_irq, wm831x_ts);
+	free_irq(wm831x_ts->data_irq, wm831x_ts);
+}
+
+static struct platform_driver wm831x_ts_driver = {
+	.driver = {
+		.name = "wm831x-touch",
+	},
+	.probe = wm831x_ts_probe,
+	.remove = wm831x_ts_remove,
+};
+module_platform_driver(wm831x_ts_driver);
+
+/* Module information */
+MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
+MODULE_DESCRIPTION("WM831x PMIC touchscreen driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:wm831x-touch");