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, 185 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/dynapro.c b/drivers/input/touchscreen/dynapro.c
new file mode 100644
index 000000000..943ba8c2f
--- /dev/null
+++ b/drivers/input/touchscreen/dynapro.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dynapro serial touchscreen driver
+ *
+ * Copyright (c) 2009 Tias Guns
+ * Based on the inexio driver (c) Vojtech Pavlik and Dan Streetman and
+ * Richard Lemon
+ */
+
+
+/*
+ * 2009/09/19 Tias Guns <tias@ulyssis.org>
+ *   Copied inexio.c and edited for Dynapro protocol (from retired Xorg module)
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"Dynapro serial touchscreen driver"
+
+MODULE_AUTHOR("Tias Guns <tias@ulyssis.org>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define DYNAPRO_FORMAT_TOUCH_BIT 0x40
+#define DYNAPRO_FORMAT_LENGTH 3
+#define DYNAPRO_RESPONSE_BEGIN_BYTE 0x80
+
+#define DYNAPRO_MIN_XC 0
+#define DYNAPRO_MAX_XC 0x3ff
+#define DYNAPRO_MIN_YC 0
+#define DYNAPRO_MAX_YC 0x3ff
+
+#define DYNAPRO_GET_XC(data) (data[1] | ((data[0] & 0x38) << 4))
+#define DYNAPRO_GET_YC(data) (data[2] | ((data[0] & 0x07) << 7))
+#define DYNAPRO_GET_TOUCHED(data) (DYNAPRO_FORMAT_TOUCH_BIT & data[0])
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct dynapro {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[DYNAPRO_FORMAT_LENGTH];
+	char phys[32];
+};
+
+static void dynapro_process_data(struct dynapro *pdynapro)
+{
+	struct input_dev *dev = pdynapro->dev;
+
+	if (DYNAPRO_FORMAT_LENGTH == ++pdynapro->idx) {
+		input_report_abs(dev, ABS_X, DYNAPRO_GET_XC(pdynapro->data));
+		input_report_abs(dev, ABS_Y, DYNAPRO_GET_YC(pdynapro->data));
+		input_report_key(dev, BTN_TOUCH,
+				 DYNAPRO_GET_TOUCHED(pdynapro->data));
+		input_sync(dev);
+
+		pdynapro->idx = 0;
+	}
+}
+
+static irqreturn_t dynapro_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct dynapro *pdynapro = serio_get_drvdata(serio);
+
+	pdynapro->data[pdynapro->idx] = data;
+
+	if (DYNAPRO_RESPONSE_BEGIN_BYTE & pdynapro->data[0])
+		dynapro_process_data(pdynapro);
+	else
+		dev_dbg(&serio->dev, "unknown/unsynchronized data: %x\n",
+			pdynapro->data[0]);
+
+	return IRQ_HANDLED;
+}
+
+static void dynapro_disconnect(struct serio *serio)
+{
+	struct dynapro *pdynapro = serio_get_drvdata(serio);
+
+	input_get_device(pdynapro->dev);
+	input_unregister_device(pdynapro->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(pdynapro->dev);
+	kfree(pdynapro);
+}
+
+/*
+ * dynapro_connect() is the routine that is called when someone adds a
+ * new serio device that supports dynapro protocol and registers it as
+ * an input device. This is usually accomplished using inputattach.
+ */
+
+static int dynapro_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct dynapro *pdynapro;
+	struct input_dev *input_dev;
+	int err;
+
+	pdynapro = kzalloc_obj(*pdynapro);
+	input_dev = input_allocate_device();
+	if (!pdynapro || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	pdynapro->serio = serio;
+	pdynapro->dev = input_dev;
+	scnprintf(pdynapro->phys, sizeof(pdynapro->phys),
+		  "%s/input0", serio->phys);
+
+	input_dev->name = "Dynapro Serial TouchScreen";
+	input_dev->phys = pdynapro->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_DYNAPRO;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0001;
+	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);
+	input_set_abs_params(pdynapro->dev, ABS_X,
+			     DYNAPRO_MIN_XC, DYNAPRO_MAX_XC, 0, 0);
+	input_set_abs_params(pdynapro->dev, ABS_Y,
+			     DYNAPRO_MIN_YC, DYNAPRO_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, pdynapro);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(pdynapro->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(pdynapro);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id dynapro_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_DYNAPRO,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, dynapro_serio_ids);
+
+static struct serio_driver dynapro_drv = {
+	.driver		= {
+		.name	= "dynapro",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= dynapro_serio_ids,
+	.interrupt	= dynapro_interrupt,
+	.connect	= dynapro_connect,
+	.disconnect	= dynapro_disconnect,
+};
+
+module_serio_driver(dynapro_drv);