sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 243 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/htcpen.c b/drivers/input/touchscreen/htcpen.c
new file mode 100644
index 000000000..056ba7608
--- /dev/null
+++ b/drivers/input/touchscreen/htcpen.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HTC Shift touchscreen driver
+ *
+ * Copyright (C) 2008 Pau Oliva Fora <pof@eslack.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/isa.h>
+#include <linux/ioport.h>
+#include <linux/dmi.h>
+
+MODULE_AUTHOR("Pau Oliva Fora <pau@eslack.org>");
+MODULE_DESCRIPTION("HTC Shift touchscreen driver");
+MODULE_LICENSE("GPL");
+
+#define HTCPEN_PORT_IRQ_CLEAR	0x068
+#define HTCPEN_PORT_INIT	0x06c
+#define HTCPEN_PORT_INDEX	0x0250
+#define HTCPEN_PORT_DATA	0x0251
+#define HTCPEN_IRQ		3
+
+#define DEVICE_ENABLE		0xa2
+#define DEVICE_DISABLE		0xa3
+
+#define X_INDEX			3
+#define Y_INDEX			5
+#define TOUCH_INDEX		0xb
+#define LSB_XY_INDEX		0xc
+#define X_AXIS_MAX		2040
+#define Y_AXIS_MAX		2040
+
+static bool invert_x;
+module_param(invert_x, bool, 0644);
+MODULE_PARM_DESC(invert_x, "If set, X axis is inverted");
+static bool invert_y;
+module_param(invert_y, bool, 0644);
+MODULE_PARM_DESC(invert_y, "If set, Y axis is inverted");
+
+static irqreturn_t htcpen_interrupt(int irq, void *handle)
+{
+	struct input_dev *htcpen_dev = handle;
+	unsigned short x, y, xy;
+
+	/* 0 = press; 1 = release */
+	outb_p(TOUCH_INDEX, HTCPEN_PORT_INDEX);
+
+	if (inb_p(HTCPEN_PORT_DATA)) {
+		input_report_key(htcpen_dev, BTN_TOUCH, 0);
+	} else {
+		outb_p(X_INDEX, HTCPEN_PORT_INDEX);
+		x = inb_p(HTCPEN_PORT_DATA);
+
+		outb_p(Y_INDEX, HTCPEN_PORT_INDEX);
+		y = inb_p(HTCPEN_PORT_DATA);
+
+		outb_p(LSB_XY_INDEX, HTCPEN_PORT_INDEX);
+		xy = inb_p(HTCPEN_PORT_DATA);
+
+		/* get high resolution value of X and Y using LSB */
+		x = X_AXIS_MAX - ((x * 8) + ((xy >> 4) & 0xf));
+		y = (y * 8) + (xy & 0xf);
+		if (invert_x)
+			x = X_AXIS_MAX - x;
+		if (invert_y)
+			y = Y_AXIS_MAX - y;
+
+		if (x != X_AXIS_MAX && x != 0) {
+			input_report_key(htcpen_dev, BTN_TOUCH, 1);
+			input_report_abs(htcpen_dev, ABS_X, x);
+			input_report_abs(htcpen_dev, ABS_Y, y);
+		}
+	}
+
+	input_sync(htcpen_dev);
+
+	inb_p(HTCPEN_PORT_IRQ_CLEAR);
+
+	return IRQ_HANDLED;
+}
+
+static int htcpen_open(struct input_dev *dev)
+{
+	outb_p(DEVICE_ENABLE, HTCPEN_PORT_INIT);
+
+	return 0;
+}
+
+static void htcpen_close(struct input_dev *dev)
+{
+	outb_p(DEVICE_DISABLE, HTCPEN_PORT_INIT);
+	synchronize_irq(HTCPEN_IRQ);
+}
+
+static int htcpen_isa_probe(struct device *dev, unsigned int id)
+{
+	struct input_dev *htcpen_dev;
+	int err = -EBUSY;
+
+	if (!request_region(HTCPEN_PORT_IRQ_CLEAR, 1, "htcpen")) {
+		printk(KERN_ERR "htcpen: unable to get IO region 0x%x\n",
+			HTCPEN_PORT_IRQ_CLEAR);
+		goto request_region1_failed;
+	}
+
+	if (!request_region(HTCPEN_PORT_INIT, 1, "htcpen")) {
+		printk(KERN_ERR "htcpen: unable to get IO region 0x%x\n",
+			HTCPEN_PORT_INIT);
+		goto request_region2_failed;
+	}
+
+	if (!request_region(HTCPEN_PORT_INDEX, 2, "htcpen")) {
+		printk(KERN_ERR "htcpen: unable to get IO region 0x%x\n",
+			HTCPEN_PORT_INDEX);
+		goto request_region3_failed;
+	}
+
+	htcpen_dev = input_allocate_device();
+	if (!htcpen_dev) {
+		printk(KERN_ERR "htcpen: can't allocate device\n");
+		err = -ENOMEM;
+		goto input_alloc_failed;
+	}
+
+	htcpen_dev->name = "HTC Shift EC TouchScreen";
+	htcpen_dev->id.bustype = BUS_ISA;
+
+	htcpen_dev->evbit[0] = BIT_MASK(EV_ABS) | BIT_MASK(EV_KEY);
+	htcpen_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+	input_set_abs_params(htcpen_dev, ABS_X, 0, X_AXIS_MAX, 0, 0);
+	input_set_abs_params(htcpen_dev, ABS_Y, 0, Y_AXIS_MAX, 0, 0);
+
+	htcpen_dev->open = htcpen_open;
+	htcpen_dev->close = htcpen_close;
+
+	err = request_irq(HTCPEN_IRQ, htcpen_interrupt, 0, "htcpen",
+			htcpen_dev);
+	if (err) {
+		printk(KERN_ERR "htcpen: irq busy\n");
+		goto request_irq_failed;
+	}
+
+	inb_p(HTCPEN_PORT_IRQ_CLEAR);
+
+	err = input_register_device(htcpen_dev);
+	if (err)
+		goto input_register_failed;
+
+	dev_set_drvdata(dev, htcpen_dev);
+
+	return 0;
+
+ input_register_failed:
+	free_irq(HTCPEN_IRQ, htcpen_dev);
+ request_irq_failed:
+	input_free_device(htcpen_dev);
+ input_alloc_failed:
+	release_region(HTCPEN_PORT_INDEX, 2);
+ request_region3_failed:
+	release_region(HTCPEN_PORT_INIT, 1);
+ request_region2_failed:
+	release_region(HTCPEN_PORT_IRQ_CLEAR, 1);
+ request_region1_failed:
+	return err;
+}
+
+static void htcpen_isa_remove(struct device *dev, unsigned int id)
+{
+	struct input_dev *htcpen_dev = dev_get_drvdata(dev);
+
+	input_unregister_device(htcpen_dev);
+
+	free_irq(HTCPEN_IRQ, htcpen_dev);
+
+	release_region(HTCPEN_PORT_INDEX, 2);
+	release_region(HTCPEN_PORT_INIT, 1);
+	release_region(HTCPEN_PORT_IRQ_CLEAR, 1);
+}
+
+#ifdef CONFIG_PM
+static int htcpen_isa_suspend(struct device *dev, unsigned int n,
+				pm_message_t state)
+{
+	outb_p(DEVICE_DISABLE, HTCPEN_PORT_INIT);
+
+	return 0;
+}
+
+static int htcpen_isa_resume(struct device *dev, unsigned int n)
+{
+	outb_p(DEVICE_ENABLE, HTCPEN_PORT_INIT);
+
+	return 0;
+}
+#endif
+
+static struct isa_driver htcpen_isa_driver = {
+	.probe		= htcpen_isa_probe,
+	.remove		= htcpen_isa_remove,
+#ifdef CONFIG_PM
+	.suspend	= htcpen_isa_suspend,
+	.resume		= htcpen_isa_resume,
+#endif
+	.driver = {
+		.owner	= THIS_MODULE,
+		.name	= "htcpen",
+	}
+};
+
+static const struct dmi_system_id htcshift_dmi_table[] __initconst = {
+	{
+		.ident = "Shift",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "High Tech Computer Corp"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Shift"),
+		},
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(dmi, htcshift_dmi_table);
+
+static int __init htcpen_isa_init(void)
+{
+	if (!dmi_check_system(htcshift_dmi_table))
+		return -ENODEV;
+
+	return isa_register_driver(&htcpen_isa_driver, 1);
+}
+
+static void __exit htcpen_isa_exit(void)
+{
+	isa_unregister_driver(&htcpen_isa_driver);
+}
+
+module_init(htcpen_isa_init);
+module_exit(htcpen_isa_exit);