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, 222 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ts4800-ts.c b/drivers/input/touchscreen/ts4800-ts.c
new file mode 100644
index 000000000..98422d1e8
--- /dev/null
+++ b/drivers/input/touchscreen/ts4800-ts.c
@@ -0,0 +1,222 @@
+/*
+ * Touchscreen driver for the TS-4800 board
+ *
+ * Copyright (c) 2015 - Savoir-faire Linux
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/bitops.h>
+#include <linux/input.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+/* polling interval in ms */
+#define POLL_INTERVAL		3
+
+#define DEBOUNCE_COUNT		1
+
+/* sensor values are 12-bit wide */
+#define MAX_12BIT		((1 << 12) - 1)
+
+#define PENDOWN_MASK		0x1
+
+#define X_OFFSET		0x0
+#define Y_OFFSET		0x2
+
+struct ts4800_ts {
+	struct input_dev        *input;
+	struct device           *dev;
+	char                    phys[32];
+
+	void __iomem            *base;
+	struct regmap           *regmap;
+	unsigned int            reg;
+	unsigned int            bit;
+
+	bool                    pendown;
+	int                     debounce;
+};
+
+static int ts4800_ts_open(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	int error;
+
+	ts->pendown = false;
+	ts->debounce = DEBOUNCE_COUNT;
+
+	error = regmap_update_bits(ts->regmap, ts->reg, ts->bit, ts->bit);
+	if (error) {
+		dev_warn(ts->dev, "Failed to enable touchscreen: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static void ts4800_ts_close(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	int ret;
+
+	ret = regmap_update_bits(ts->regmap, ts->reg, ts->bit, 0);
+	if (ret)
+		dev_warn(ts->dev, "Failed to disable touchscreen\n");
+
+}
+
+static void ts4800_ts_poll(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	u16 last_x = readw(ts->base + X_OFFSET);
+	u16 last_y = readw(ts->base + Y_OFFSET);
+	bool pendown = last_x & PENDOWN_MASK;
+
+	if (pendown) {
+		if (ts->debounce) {
+			ts->debounce--;
+			return;
+		}
+
+		if (!ts->pendown) {
+			input_report_key(input_dev, BTN_TOUCH, 1);
+			ts->pendown = true;
+		}
+
+		last_x = ((~last_x) >> 4) & MAX_12BIT;
+		last_y = ((~last_y) >> 4) & MAX_12BIT;
+
+		input_report_abs(input_dev, ABS_X, last_x);
+		input_report_abs(input_dev, ABS_Y, last_y);
+		input_sync(input_dev);
+	} else if (ts->pendown) {
+		ts->pendown = false;
+		ts->debounce = DEBOUNCE_COUNT;
+		input_report_key(input_dev, BTN_TOUCH, 0);
+		input_sync(input_dev);
+	}
+}
+
+static int ts4800_parse_dt(struct platform_device *pdev,
+			   struct ts4800_ts *ts)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	u32 reg, bit;
+	int error;
+
+	struct device_node *syscon_np __free(device_node) =
+		of_parse_phandle(np, "syscon", 0);
+	if (!syscon_np) {
+		dev_err(dev, "no syscon property\n");
+		return -ENODEV;
+	}
+
+	ts->regmap = syscon_node_to_regmap(syscon_np);
+	if (IS_ERR(ts->regmap)) {
+		dev_err(dev, "cannot get parent's regmap\n");
+		return PTR_ERR(ts->regmap);
+	}
+
+	error = of_property_read_u32_index(np, "syscon", 1, &reg);
+	if (error < 0) {
+		dev_err(dev, "no offset in syscon\n");
+		return error;
+	}
+
+	ts->reg = reg;
+
+	error = of_property_read_u32_index(np, "syscon", 2, &bit);
+	if (error < 0) {
+		dev_err(dev, "no bit in syscon\n");
+		return error;
+	}
+
+	ts->bit = BIT(bit);
+
+	return 0;
+}
+
+static int ts4800_ts_probe(struct platform_device *pdev)
+{
+	struct input_dev *input_dev;
+	struct ts4800_ts *ts;
+	int error;
+
+	ts = devm_kzalloc(&pdev->dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	error = ts4800_parse_dt(pdev, ts);
+	if (error)
+		return error;
+
+	ts->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ts->base))
+		return PTR_ERR(ts->base);
+
+	input_dev = devm_input_allocate_device(&pdev->dev);
+	if (!input_dev)
+		return -ENOMEM;
+
+	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&pdev->dev));
+	ts->input = input_dev;
+	ts->dev = &pdev->dev;
+
+	input_set_drvdata(input_dev, ts);
+
+	input_dev->name = "TS-4800 Touchscreen";
+	input_dev->phys = ts->phys;
+
+	input_dev->open = ts4800_ts_open;
+	input_dev->close = ts4800_ts_close;
+
+	input_set_capability(input_dev, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input_dev, ABS_X, 0, MAX_12BIT, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, MAX_12BIT, 0, 0);
+
+	error = input_setup_polling(input_dev, ts4800_ts_poll);
+	if (error) {
+		dev_err(&pdev->dev, "Unable to set up polling: %d\n", error);
+		return error;
+	}
+
+	input_set_poll_interval(input_dev, POLL_INTERVAL);
+
+	error = input_register_device(input_dev);
+	if (error) {
+		dev_err(&pdev->dev,
+			"Unable to register input device: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id ts4800_ts_of_match[] = {
+	{ .compatible = "technologic,ts4800-ts", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ts4800_ts_of_match);
+
+static struct platform_driver ts4800_ts_driver = {
+	.driver = {
+		.name = "ts4800-ts",
+		.of_match_table = ts4800_ts_of_match,
+	},
+	.probe = ts4800_ts_probe,
+};
+module_platform_driver(ts4800_ts_driver);
+
+MODULE_AUTHOR("Damien Riegel <damien.riegel@savoirfairelinux.com>");
+MODULE_DESCRIPTION("TS-4800 Touchscreen Driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:ts4800_ts");