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, 340 insertions, 0 deletions

diff --git a/drivers/input/mouse/sermouse.c b/drivers/input/mouse/sermouse.c
new file mode 100644
index 000000000..c334a4887
--- /dev/null
+++ b/drivers/input/mouse/sermouse.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1999-2001 Vojtech Pavlik
+ */
+
+/*
+ *  Serial mouse driver for Linux
+ */
+
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"Serial mouse driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+static const char *sermouse_protocols[] = { "None", "Mouse Systems Mouse", "Sun Mouse", "Microsoft Mouse",
+					"Logitech M+ Mouse", "Microsoft MZ Mouse", "Logitech MZ+ Mouse",
+					"Logitech MZ++ Mouse"};
+
+struct sermouse {
+	struct input_dev *dev;
+	signed char buf[8];
+	unsigned char count;
+	unsigned char type;
+	unsigned long last;
+	char phys[32];
+};
+
+/*
+ * sermouse_process_msc() analyzes the incoming MSC/Sun bytestream and
+ * applies some prediction to the data, resulting in 96 updates per
+ * second, which is as good as a PS/2 or USB mouse.
+ */
+
+static void sermouse_process_msc(struct sermouse *sermouse, signed char data)
+{
+	struct input_dev *dev = sermouse->dev;
+	signed char *buf = sermouse->buf;
+
+	switch (sermouse->count) {
+
+		case 0:
+			if ((data & 0xf8) != 0x80)
+				return;
+			input_report_key(dev, BTN_LEFT,   !(data & 4));
+			input_report_key(dev, BTN_RIGHT,  !(data & 1));
+			input_report_key(dev, BTN_MIDDLE, !(data & 2));
+			break;
+
+		case 1:
+		case 3:
+			input_report_rel(dev, REL_X, data / 2);
+			input_report_rel(dev, REL_Y, -buf[1]);
+			buf[0] = data - data / 2;
+			break;
+
+		case 2:
+		case 4:
+			input_report_rel(dev, REL_X, buf[0]);
+			input_report_rel(dev, REL_Y, buf[1] - data);
+			buf[1] = data / 2;
+			break;
+	}
+
+	input_sync(dev);
+
+	if (++sermouse->count == 5)
+		sermouse->count = 0;
+}
+
+/*
+ * sermouse_process_ms() anlyzes the incoming MS(Z/+/++) bytestream and
+ * generates events. With prediction it gets 80 updates/sec, assuming
+ * standard 3-byte packets and 1200 bps.
+ */
+
+static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
+{
+	struct input_dev *dev = sermouse->dev;
+	signed char *buf = sermouse->buf;
+
+	if (data & 0x40)
+		sermouse->count = 0;
+	else if (sermouse->count == 0)
+		return;
+
+	switch (sermouse->count) {
+
+		case 0:
+			buf[1] = data;
+			input_report_key(dev, BTN_LEFT,   (data >> 5) & 1);
+			input_report_key(dev, BTN_RIGHT,  (data >> 4) & 1);
+			break;
+
+		case 1:
+			buf[2] = data;
+			data = (signed char) (((buf[1] << 6) & 0xc0) | (data & 0x3f));
+			input_report_rel(dev, REL_X, data / 2);
+			input_report_rel(dev, REL_Y, buf[4]);
+			buf[3] = data - data / 2;
+			break;
+
+		case 2:
+			/* Guessing the state of the middle button on 3-button MS-protocol mice - ugly. */
+			if ((sermouse->type == SERIO_MS) && !data && !buf[2] && !((buf[0] & 0xf0) ^ buf[1]))
+				input_report_key(dev, BTN_MIDDLE, !test_bit(BTN_MIDDLE, dev->key));
+			buf[0] = buf[1];
+
+			data = (signed char) (((buf[1] << 4) & 0xc0) | (data & 0x3f));
+			input_report_rel(dev, REL_X, buf[3]);
+			input_report_rel(dev, REL_Y, data - buf[4]);
+			buf[4] = data / 2;
+			break;
+
+		case 3:
+
+			switch (sermouse->type) {
+
+				case SERIO_MS:
+					sermouse->type = SERIO_MP;
+					fallthrough;
+
+				case SERIO_MP:
+					if ((data >> 2) & 3) break;	/* M++ Wireless Extension packet. */
+					input_report_key(dev, BTN_MIDDLE, (data >> 5) & 1);
+					input_report_key(dev, BTN_SIDE,   (data >> 4) & 1);
+					break;
+
+				case SERIO_MZP:
+				case SERIO_MZPP:
+					input_report_key(dev, BTN_SIDE,   (data >> 5) & 1);
+					fallthrough;
+
+				case SERIO_MZ:
+					input_report_key(dev, BTN_MIDDLE, (data >> 4) & 1);
+					input_report_rel(dev, REL_WHEEL,  (data & 8) - (data & 7));
+					break;
+			}
+
+			break;
+
+		case 4:
+		case 6:	/* MZ++ packet type. We can get these bytes for M++ too but we ignore them later. */
+			buf[1] = (data >> 2) & 0x0f;
+			break;
+
+		case 5:
+		case 7: /* Ignore anything besides MZ++ */
+			if (sermouse->type != SERIO_MZPP)
+				break;
+
+			switch (buf[1]) {
+
+				case 1: /* Extra mouse info */
+
+					input_report_key(dev, BTN_SIDE, (data >> 4) & 1);
+					input_report_key(dev, BTN_EXTRA, (data >> 5) & 1);
+					input_report_rel(dev, data & 0x80 ? REL_HWHEEL : REL_WHEEL, (data & 7) - (data & 8));
+
+					break;
+
+				default: /* We don't decode anything else yet. */
+
+					printk(KERN_WARNING
+						"sermouse.c: Received MZ++ packet %x, don't know how to handle.\n", buf[1]);
+					break;
+			}
+
+			break;
+	}
+
+	input_sync(dev);
+
+	sermouse->count++;
+}
+
+/*
+ * sermouse_interrupt() handles incoming characters, either gathering them into
+ * packets or passing them to the command routine as command output.
+ */
+
+static irqreturn_t sermouse_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct sermouse *sermouse = serio_get_drvdata(serio);
+
+	if (time_after(jiffies, sermouse->last + HZ/10))
+		sermouse->count = 0;
+
+	sermouse->last = jiffies;
+
+	if (sermouse->type > SERIO_SUN)
+		sermouse_process_ms(sermouse, data);
+	else
+		sermouse_process_msc(sermouse, data);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * sermouse_disconnect() cleans up after we don't want talk
+ * to the mouse anymore.
+ */
+
+static void sermouse_disconnect(struct serio *serio)
+{
+	struct sermouse *sermouse = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(sermouse->dev);
+	kfree(sermouse);
+}
+
+/*
+ * sermouse_connect() is a callback form the serio module when
+ * an unhandled serio port is found.
+ */
+
+static int sermouse_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct sermouse *sermouse;
+	struct input_dev *input_dev;
+	unsigned char c = serio->id.extra;
+	int err = -ENOMEM;
+
+	sermouse = kzalloc_obj(*sermouse);
+	input_dev = input_allocate_device();
+	if (!sermouse || !input_dev)
+		goto fail1;
+
+	sermouse->dev = input_dev;
+	snprintf(sermouse->phys, sizeof(sermouse->phys), "%s/input0", serio->phys);
+	sermouse->type = serio->id.proto;
+
+	input_dev->name = sermouse_protocols[sermouse->type];
+	input_dev->phys = sermouse->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor  = sermouse->type;
+	input_dev->id.product = c;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	input_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_RIGHT);
+	input_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+
+	if (c & 0x01) set_bit(BTN_MIDDLE, input_dev->keybit);
+	if (c & 0x02) set_bit(BTN_SIDE, input_dev->keybit);
+	if (c & 0x04) set_bit(BTN_EXTRA, input_dev->keybit);
+	if (c & 0x10) set_bit(REL_WHEEL, input_dev->relbit);
+	if (c & 0x20) set_bit(REL_HWHEEL, input_dev->relbit);
+
+	serio_set_drvdata(serio, sermouse);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(sermouse->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(sermouse);
+	return err;
+}
+
+static struct serio_device_id sermouse_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MSC,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_SUN,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MS,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MP,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MZ,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MZP,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MZPP,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, sermouse_serio_ids);
+
+static struct serio_driver sermouse_drv = {
+	.driver		= {
+		.name	= "sermouse",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= sermouse_serio_ids,
+	.interrupt	= sermouse_interrupt,
+	.connect	= sermouse_connect,
+	.disconnect	= sermouse_disconnect,
+};
+
+module_serio_driver(sermouse_drv);