platform/x86: Add ACPI quickstart button (PNP0C32) driver

This drivers supports the ACPI quickstart button device, which
is used to send manufacturer-specific events to userspace.
Since the meaning of those events is not standardized, userspace
has to use for example hwdb to decode them.

The driver itself is based on an earlier proposal, but contains
some improvements and uses the device wakeup API instead of a
custom sysfs file.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20240131111641.4418-2-W_Armin@gmx.de
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

MAINTAINERS

@@ -360,6 +360,12 @@ B:	https://bugzilla.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
 F:	drivers/acpi/pmic/
 
+ACPI QUICKSTART DRIVER
+M:	Armin Wolf <W_Armin@gmx.de>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/quickstart.c
+
 ACPI SERIAL MULTI INSTANTIATE DRIVER
 M:	Hans de Goede <hdegoede@redhat.com>
 L:	platform-driver-x86@vger.kernel.org

drivers/platform/x86/Kconfig

@@ -642,6 +642,19 @@ config THINKPAD_LMI
 
 source "drivers/platform/x86/intel/Kconfig"
 
+config ACPI_QUICKSTART
+	tristate "ACPI Quickstart button driver"
+	depends on ACPI
+	depends on INPUT
+	select INPUT_SPARSE_KEYMAP
+	help
+	  This driver adds support for ACPI quickstart button (PNP0C32) devices.
+	  The button emits a manufacturer-specific key value when pressed, so
+	  userspace has to map this value to a standard key code.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called quickstart.
+
 config MSI_EC
 	tristate "MSI EC Extras"
 	depends on ACPI

drivers/platform/x86/Makefile

@@ -71,6 +71,9 @@ obj-$(CONFIG_LENOVO_WMI_CAMERA)	+= lenovo-wmi-camera.o
 # Intel
 obj-y				+= intel/
 
+# Microsoft
+obj-$(CONFIG_ACPI_QUICKSTART)  += quickstart.o
+
 # MSI
 obj-$(CONFIG_MSI_EC)		+= msi-ec.o
 obj-$(CONFIG_MSI_LAPTOP)	+= msi-laptop.o

drivers/platform/x86/quickstart.c

@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * quickstart.c - ACPI Direct App Launch driver
+ *
+ * Copyright (C) 2024 Armin Wolf <W_Armin@gmx.de>
+ * Copyright (C) 2022 Arvid Norlander <lkml@vorapal.se>
+ * Copyright (C) 2007-2010 Angelo Arrifano <miknix@gmail.com>
+ *
+ * Information gathered from disassembled dsdt and from here:
+ * <https://archive.org/details/microsoft-acpi-dirapplaunch>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/input/sparse-keymap.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
+
+#define DRIVER_NAME	"quickstart"
+
+/*
+ * There will be two events:
+ * 0x02 - Button was pressed while device was off/sleeping.
+ * 0x80 - Button was pressed while device was up.
+ */
+#define QUICKSTART_EVENT_RUNTIME	0x80
+
+struct quickstart_data {
+	struct device *dev;
+	struct input_dev *input_device;
+	char input_name[32];
+	char phys[32];
+	u32 id;
+};
+
+/*
+ * Knowing what these buttons do require system specific knowledge.
+ * This could be done by matching on DMI data in a long quirk table.
+ * However, it is easier to leave it up to user space to figure this out.
+ *
+ * Using for example udev hwdb the scancode 0x1 can be remapped suitably.
+ */
+static const struct key_entry quickstart_keymap[] = {
+	{ KE_KEY, 0x1, { KEY_UNKNOWN } },
+	{ KE_END, 0 },
+};
+
+static ssize_t button_id_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct quickstart_data *data = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", data->id);
+}
+static DEVICE_ATTR_RO(button_id);
+
+static struct attribute *quickstart_attrs[] = {
+	&dev_attr_button_id.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(quickstart);
+
+static void quickstart_notify(acpi_handle handle, u32 event, void *context)
+{
+	struct quickstart_data *data = context;
+
+	switch (event) {
+	case QUICKSTART_EVENT_RUNTIME:
+		sparse_keymap_report_event(data->input_device, 0x1, 1, true);
+		acpi_bus_generate_netlink_event(DRIVER_NAME, dev_name(data->dev), event, 0);
+		break;
+	default:
+		dev_err(data->dev, FW_INFO "Unexpected ACPI notify event (%u)\n", event);
+		break;
+	}
+}
+
+/*
+ * The GHID ACPI method is used to indicate the "role" of the button.
+ * However, all the meanings of these values are vendor defined.
+ *
+ * We do however expose this value to user space.
+ */
+static int quickstart_get_ghid(struct quickstart_data *data)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	acpi_handle handle = ACPI_HANDLE(data->dev);
+	union acpi_object *obj;
+	acpi_status status;
+	int ret = 0;
+
+	/*
+	 * This returns a buffer telling the button usage ID,
+	 * and triggers pending notify events (The ones before booting).
+	 */
+	status = acpi_evaluate_object_typed(handle, "GHID", NULL, &buffer, ACPI_TYPE_BUFFER);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	obj = buffer.pointer;
+	if (!obj)
+		return -ENODATA;
+
+	/*
+	 * Quoting the specification:
+	 * "The GHID method can return a BYTE, WORD, or DWORD.
+	 *  The value must be encoded in little-endian byte
+	 *  order (least significant byte first)."
+	 */
+	switch (obj->buffer.length) {
+	case 1:
+		data->id = obj->buffer.pointer[0];
+		break;
+	case 2:
+		data->id = get_unaligned_le16(obj->buffer.pointer);
+		break;
+	case 4:
+		data->id = get_unaligned_le32(obj->buffer.pointer);
+		break;
+	default:
+		dev_err(data->dev,
+			FW_BUG "GHID method returned buffer of unexpected length %u\n",
+			obj->buffer.length);
+		ret = -EIO;
+		break;
+	}
+
+	kfree(obj);
+
+	return ret;
+}
+
+static void quickstart_notify_remove(void *context)
+{
+	struct quickstart_data *data = context;
+	acpi_handle handle;
+
+	handle = ACPI_HANDLE(data->dev);
+
+	acpi_remove_notify_handler(handle, ACPI_DEVICE_NOTIFY, quickstart_notify);
+}
+
+static int quickstart_probe(struct platform_device *pdev)
+{
+	struct quickstart_data *data;
+	acpi_handle handle;
+	acpi_status status;
+	int ret;
+
+	handle = ACPI_HANDLE(&pdev->dev);
+	if (!handle)
+		return -ENODEV;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->dev = &pdev->dev;
+	dev_set_drvdata(&pdev->dev, data);
+
+	/* We have to initialize the device wakeup before evaluating GHID because
+	 * doing so will notify the device if the button was used to wake the machine
+	 * from S5.
+	 */
+	device_init_wakeup(&pdev->dev, true);
+
+	ret = quickstart_get_ghid(data);
+	if (ret < 0)
+		return ret;
+
+	data->input_device = devm_input_allocate_device(&pdev->dev);
+	if (!data->input_device)
+		return -ENOMEM;
+
+	ret = sparse_keymap_setup(data->input_device, quickstart_keymap, NULL);
+	if (ret < 0)
+		return ret;
+
+	snprintf(data->input_name, sizeof(data->input_name), "Quickstart Button %u", data->id);
+	snprintf(data->phys, sizeof(data->phys), DRIVER_NAME "/input%u", data->id);
+
+	data->input_device->name = data->input_name;
+	data->input_device->phys = data->phys;
+	data->input_device->id.bustype = BUS_HOST;
+
+	ret = input_register_device(data->input_device);
+	if (ret < 0)
+		return ret;
+
+	status = acpi_install_notify_handler(handle, ACPI_DEVICE_NOTIFY, quickstart_notify, data);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	return devm_add_action_or_reset(&pdev->dev, quickstart_notify_remove, data);
+}
+
+static const struct acpi_device_id quickstart_device_ids[] = {
+	{ "PNP0C32", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, quickstart_device_ids);
+
+static struct platform_driver quickstart_platform_driver = {
+	.driver	= {
+		.name = DRIVER_NAME,
+		.dev_groups = quickstart_groups,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.acpi_match_table = quickstart_device_ids,
+	},
+	.probe = quickstart_probe,
+};
+module_platform_driver(quickstart_platform_driver);
+
+MODULE_AUTHOR("Armin Wolf <W_Armin@gmx.de>");
+MODULE_AUTHOR("Arvid Norlander <lkml@vorpal.se>");
+MODULE_AUTHOR("Angelo Arrifano");
+MODULE_DESCRIPTION("ACPI Direct App Launch driver");
+MODULE_LICENSE("GPL");