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, 315 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/penmount.c b/drivers/input/touchscreen/penmount.c
new file mode 100644
index 000000000..4b57b6664
--- /dev/null
+++ b/drivers/input/touchscreen/penmount.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Penmount serial touchscreen driver
+ *
+ * Copyright (c) 2006 Rick Koch <n1gp@hotmail.com>
+ * Copyright (c) 2011 John Sung <penmount.touch@gmail.com>
+ *
+ * Based on ELO driver (drivers/input/touchscreen/elo.c)
+ * Copyright (c) 2004 Vojtech Pavlik
+ */
+
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"PenMount serial touchscreen driver"
+
+MODULE_AUTHOR("Rick Koch <n1gp@hotmail.com>");
+MODULE_AUTHOR("John Sung <penmount.touch@gmail.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define	PM_MAX_LENGTH	6
+#define	PM_MAX_MTSLOT	16
+#define	PM_3000_MTSLOT	2
+#define	PM_6250_MTSLOT	12
+
+/*
+ * Multi-touch slot
+ */
+
+struct mt_slot {
+	unsigned short x, y;
+	bool active; /* is the touch valid? */
+};
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct pm {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[PM_MAX_LENGTH];
+	char phys[32];
+	unsigned char packetsize;
+	unsigned char maxcontacts;
+	struct mt_slot slots[PM_MAX_MTSLOT];
+	void (*parse_packet)(struct pm *);
+};
+
+/*
+ * pm_mtevent() sends mt events and also emulates pointer movement
+ */
+
+static void pm_mtevent(struct pm *pm, struct input_dev *input)
+{
+	int i;
+
+	for (i = 0; i < pm->maxcontacts; ++i) {
+		input_mt_slot(input, i);
+		input_mt_report_slot_state(input, MT_TOOL_FINGER,
+				pm->slots[i].active);
+		if (pm->slots[i].active) {
+			input_event(input, EV_ABS, ABS_MT_POSITION_X, pm->slots[i].x);
+			input_event(input, EV_ABS, ABS_MT_POSITION_Y, pm->slots[i].y);
+		}
+	}
+
+	input_mt_report_pointer_emulation(input, true);
+	input_sync(input);
+}
+
+/*
+ * pm_checkpacket() checks if data packet is valid
+ */
+
+static bool pm_checkpacket(unsigned char *packet)
+{
+	int total = 0;
+	int i;
+
+	for (i = 0; i < 5; i++)
+		total += packet[i];
+
+	return packet[5] == (unsigned char)~(total & 0xff);
+}
+
+static void pm_parse_9000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0x80) && pm->packetsize == ++pm->idx) {
+		input_report_abs(dev, ABS_X, pm->data[1] * 128 + pm->data[2]);
+		input_report_abs(dev, ABS_Y, pm->data[3] * 128 + pm->data[4]);
+		input_report_key(dev, BTN_TOUCH, !!(pm->data[0] & 0x40));
+		input_sync(dev);
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_6000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xbf) == 0x30 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			input_report_abs(dev, ABS_X,
+					pm->data[2] * 256 + pm->data[1]);
+			input_report_abs(dev, ABS_Y,
+					pm->data[4] * 256 + pm->data[3]);
+			input_report_key(dev, BTN_TOUCH, pm->data[0] & 0x40);
+			input_sync(dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_3000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xce) == 0x40 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			int slotnum = pm->data[0] & 0x0f;
+			pm->slots[slotnum].active = pm->data[0] & 0x30;
+			pm->slots[slotnum].x = pm->data[2] * 256 + pm->data[1];
+			pm->slots[slotnum].y = pm->data[4] * 256 + pm->data[3];
+			pm_mtevent(pm, dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_6250(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xb0) == 0x30 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			int slotnum = pm->data[0] & 0x0f;
+			pm->slots[slotnum].active = pm->data[0] & 0x40;
+			pm->slots[slotnum].x = pm->data[2] * 256 + pm->data[1];
+			pm->slots[slotnum].y = pm->data[4] * 256 + pm->data[3];
+			pm_mtevent(pm, dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static irqreturn_t pm_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct pm *pm = serio_get_drvdata(serio);
+
+	pm->data[pm->idx] = data;
+
+	pm->parse_packet(pm);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * pm_disconnect() is the opposite of pm_connect()
+ */
+
+static void pm_disconnect(struct serio *serio)
+{
+	struct pm *pm = serio_get_drvdata(serio);
+
+	serio_close(serio);
+
+	input_unregister_device(pm->dev);
+	kfree(pm);
+
+	serio_set_drvdata(serio, NULL);
+}
+
+/*
+ * pm_connect() is the routine that is called when someone adds a
+ * new serio device that supports PenMount protocol and registers it as
+ * an input device.
+ */
+
+static int pm_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct pm *pm;
+	struct input_dev *input_dev;
+	int max_x, max_y;
+	int err;
+
+	pm = kzalloc_obj(*pm);
+	input_dev = input_allocate_device();
+	if (!pm || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	pm->serio = serio;
+	pm->dev = input_dev;
+	scnprintf(pm->phys, sizeof(pm->phys), "%s/input0", serio->phys);
+	pm->maxcontacts = 1;
+
+	input_dev->name = "PenMount Serial TouchScreen";
+	input_dev->phys = pm->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_PENMOUNT;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+
+	switch (serio->id.id) {
+	default:
+	case 0:
+		pm->packetsize = 5;
+		pm->parse_packet = pm_parse_9000;
+		input_dev->id.product = 0x9000;
+		max_x = max_y = 0x3ff;
+		break;
+
+	case 1:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_6000;
+		input_dev->id.product = 0x6000;
+		max_x = max_y = 0x3ff;
+		break;
+
+	case 2:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_3000;
+		input_dev->id.product = 0x3000;
+		max_x = max_y = 0x7ff;
+		pm->maxcontacts = PM_3000_MTSLOT;
+		break;
+
+	case 3:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_6250;
+		input_dev->id.product = 0x6250;
+		max_x = max_y = 0x3ff;
+		pm->maxcontacts = PM_6250_MTSLOT;
+		break;
+	}
+
+	input_set_abs_params(pm->dev, ABS_X, 0, max_x, 0, 0);
+	input_set_abs_params(pm->dev, ABS_Y, 0, max_y, 0, 0);
+
+	if (pm->maxcontacts > 1) {
+		input_mt_init_slots(pm->dev, pm->maxcontacts, 0);
+		input_set_abs_params(pm->dev,
+				     ABS_MT_POSITION_X, 0, max_x, 0, 0);
+		input_set_abs_params(pm->dev,
+				     ABS_MT_POSITION_Y, 0, max_y, 0, 0);
+	}
+
+	serio_set_drvdata(serio, pm);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(pm->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(pm);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id pm_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_PENMOUNT,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, pm_serio_ids);
+
+static struct serio_driver pm_drv = {
+	.driver		= {
+		.name	= "serio-penmount",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= pm_serio_ids,
+	.interrupt	= pm_interrupt,
+	.connect	= pm_connect,
+	.disconnect	= pm_disconnect,
+};
+
+module_serio_driver(pm_drv);