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, 208 insertions, 0 deletions

diff --git a/drivers/input/touchscreen.c b/drivers/input/touchscreen.c
new file mode 100644
index 000000000..d699b24bb
--- /dev/null
+++ b/drivers/input/touchscreen.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Generic helper functions for touchscreens and other two-dimensional
+ *  pointing devices
+ *
+ *  Copyright (c) 2014 Sebastian Reichel <sre@kernel.org>
+ */
+
+#include <linux/export.h>
+#include <linux/property.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/module.h>
+
+static bool touchscreen_get_prop_u32(struct device *dev,
+				     const char *property,
+				     unsigned int default_value,
+				     unsigned int *value)
+{
+	u32 val;
+	int error;
+
+	error = device_property_read_u32(dev, property, &val);
+	if (error) {
+		*value = default_value;
+		return false;
+	}
+
+	*value = val;
+	return true;
+}
+
+static void touchscreen_set_params(struct input_dev *dev,
+				   unsigned long axis,
+				   int min, int max, int fuzz)
+{
+	struct input_absinfo *absinfo;
+
+	if (!test_bit(axis, dev->absbit)) {
+		dev_warn(&dev->dev,
+			 "Parameters are specified but the axis %lu is not set up\n",
+			 axis);
+		return;
+	}
+
+	absinfo = &dev->absinfo[axis];
+	absinfo->minimum = min;
+	absinfo->maximum = max;
+	absinfo->fuzz = fuzz;
+}
+
+/**
+ * touchscreen_parse_properties - parse common touchscreen properties
+ * @input: input device that should be parsed
+ * @multitouch: specifies whether parsed properties should be applied to
+ *	single-touch or multi-touch axes
+ * @prop: pointer to a struct touchscreen_properties into which to store
+ *	axis swap and invert info for use with touchscreen_report_x_y();
+ *	or %NULL
+ *
+ * This function parses common properties for touchscreens and sets up the
+ * input device accordingly. The function keeps previously set up default
+ * values if no value is specified.
+ */
+void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
+				  struct touchscreen_properties *prop)
+{
+	struct device *dev = input->dev.parent;
+	struct input_absinfo *absinfo;
+	unsigned int axis, axis_x, axis_y;
+	unsigned int minimum, maximum, fuzz;
+	bool data_present;
+
+	input_alloc_absinfo(input);
+	if (!input->absinfo)
+		return;
+
+	axis_x = multitouch ? ABS_MT_POSITION_X : ABS_X;
+	axis_y = multitouch ? ABS_MT_POSITION_Y : ABS_Y;
+
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
+						input_abs_get_min(input, axis_x),
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-x",
+						 input_abs_get_max(input,
+								   axis_x) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
+						 input_abs_get_fuzz(input, axis_x),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis_x, minimum, maximum - 1, fuzz);
+
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-y",
+						input_abs_get_min(input, axis_y),
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-y",
+						 input_abs_get_max(input,
+								   axis_y) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
+						 input_abs_get_fuzz(input, axis_y),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis_y, minimum, maximum - 1, fuzz);
+
+	axis = multitouch ? ABS_MT_PRESSURE : ABS_PRESSURE;
+	data_present = touchscreen_get_prop_u32(dev,
+						"touchscreen-max-pressure",
+						input_abs_get_max(input, axis),
+						&maximum);
+	data_present |= touchscreen_get_prop_u32(dev,
+						 "touchscreen-fuzz-pressure",
+						 input_abs_get_fuzz(input, axis),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis, 0, maximum, fuzz);
+
+	if (!prop)
+		return;
+
+	prop->max_x = input_abs_get_max(input, axis_x);
+	prop->max_y = input_abs_get_max(input, axis_y);
+
+	prop->invert_x =
+		device_property_read_bool(dev, "touchscreen-inverted-x");
+	if (prop->invert_x) {
+		absinfo = &input->absinfo[axis_x];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
+	prop->invert_y =
+		device_property_read_bool(dev, "touchscreen-inverted-y");
+	if (prop->invert_y) {
+		absinfo = &input->absinfo[axis_y];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
+	prop->swap_x_y =
+		device_property_read_bool(dev, "touchscreen-swapped-x-y");
+	if (prop->swap_x_y)
+		swap(input->absinfo[axis_x], input->absinfo[axis_y]);
+}
+EXPORT_SYMBOL(touchscreen_parse_properties);
+
+static void
+touchscreen_apply_prop_to_x_y(const struct touchscreen_properties *prop,
+			      unsigned int *x, unsigned int *y)
+{
+	if (prop->invert_x)
+		*x = prop->max_x - *x;
+
+	if (prop->invert_y)
+		*y = prop->max_y - *y;
+
+	if (prop->swap_x_y)
+		swap(*x, *y);
+}
+
+/**
+ * touchscreen_set_mt_pos - Set input_mt_pos coordinates
+ * @pos: input_mt_pos to set coordinates of
+ * @prop: pointer to a struct touchscreen_properties
+ * @x: X coordinate to store in pos
+ * @y: Y coordinate to store in pos
+ *
+ * Adjust the passed in x and y values applying any axis inversion and
+ * swapping requested in the passed in touchscreen_properties and store
+ * the result in a struct input_mt_pos.
+ */
+void touchscreen_set_mt_pos(struct input_mt_pos *pos,
+			    const struct touchscreen_properties *prop,
+			    unsigned int x, unsigned int y)
+{
+	touchscreen_apply_prop_to_x_y(prop, &x, &y);
+	pos->x = x;
+	pos->y = y;
+}
+EXPORT_SYMBOL(touchscreen_set_mt_pos);
+
+/**
+ * touchscreen_report_pos - Report touchscreen coordinates
+ * @input: input_device to report coordinates for
+ * @prop: pointer to a struct touchscreen_properties
+ * @x: X coordinate to report
+ * @y: Y coordinate to report
+ * @multitouch: Report coordinates on single-touch or multi-touch axes
+ *
+ * Adjust the passed in x and y values applying any axis inversion and
+ * swapping requested in the passed in touchscreen_properties and then
+ * report the resulting coordinates on the input_dev's x and y axis.
+ */
+void touchscreen_report_pos(struct input_dev *input,
+			    const struct touchscreen_properties *prop,
+			    unsigned int x, unsigned int y,
+			    bool multitouch)
+{
+	touchscreen_apply_prop_to_x_y(prop, &x, &y);
+	input_report_abs(input, multitouch ? ABS_MT_POSITION_X : ABS_X, x);
+	input_report_abs(input, multitouch ? ABS_MT_POSITION_Y : ABS_Y, y);
+}
+EXPORT_SYMBOL(touchscreen_report_pos);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Helper functions for touchscreens and other devices");