platform/x86/tuxedo: Add virtual LampArray for TUXEDO NB04 devices

The TUXEDO Sirius 16 Gen1 and TUXEDO Sirius 16 Gen2 devices have a per-key
controllable RGB keyboard backlight. The firmware API for it is implemented
via WMI.

To make the backlight userspace configurable this driver emulates a
LampArray HID device and translates the input from hidraw to the
corresponding WMI calls. This is a new approach as the leds subsystem lacks
a suitable UAPI for per-key keyboard backlights, and like this no new UAPI
needs to be established.

The handle_* functions an corresponding structs are named based on the HID
spec: HID Usage Tables 1.6 -> 26 Lighting And Illumination Page (0x59)

Signed-off-by: Werner Sembach <wse@tuxedocomputers.com>
Link: https://lore.kernel.org/r/20250425210043.342288-2-wse@tuxedocomputers.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/drivers/platform/x86/tuxedo/nb04/wmi_util.c b/drivers/platform/x86/tuxedo/nb04/wmi_util.c
new file mode 100644
index 000000000000..e894690da1a8
--- /dev/null
+++ b/drivers/platform/x86/tuxedo/nb04/wmi_util.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This code gives functions to avoid code duplication while interacting with
+ * the TUXEDO NB04 wmi interfaces.
+ *
+ * Copyright (C) 2024-2025 Werner Sembach <wse@tuxedocomputers.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cleanup.h>
+#include <linux/wmi.h>
+
+#include "wmi_util.h"
+
+static int __wmi_method_acpi_object_out(struct wmi_device *wdev,
+					u32 wmi_method_id,
+					u8 *in,
+					acpi_size in_len,
+					union acpi_object **out)
+{
+	struct acpi_buffer acpi_buffer_in = { in_len, in };
+	struct acpi_buffer acpi_buffer_out = { ACPI_ALLOCATE_BUFFER, NULL };
+
+	dev_dbg(&wdev->dev, "Evaluate WMI method: %u in:\n", wmi_method_id);
+	print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, in, in_len);
+
+	acpi_status status = wmidev_evaluate_method(wdev, 0, wmi_method_id,
+						    &acpi_buffer_in,
+						    &acpi_buffer_out);
+	if (ACPI_FAILURE(status)) {
+		dev_err(&wdev->dev, "Failed to evaluate WMI method.\n");
+		return -EIO;
+	}
+	if (!acpi_buffer_out.pointer) {
+		dev_err(&wdev->dev, "Unexpected empty out buffer.\n");
+		return -ENODATA;
+	}
+
+	*out = acpi_buffer_out.pointer;
+
+	return 0;
+}
+
+static int __wmi_method_buffer_out(struct wmi_device *wdev,
+				   u32 wmi_method_id,
+				   u8 *in,
+				   acpi_size in_len,
+				   u8 *out,
+				   acpi_size out_len)
+{
+	int ret;
+
+	union acpi_object *acpi_object_out __free(kfree) = NULL;
+
+	ret = __wmi_method_acpi_object_out(wdev, wmi_method_id,
+					   in, in_len,
+					   &acpi_object_out);
+	if (ret)
+		return ret;
+
+	if (acpi_object_out->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Unexpected out buffer type. Expected: %u Got: %u\n",
+			ACPI_TYPE_BUFFER, acpi_object_out->type);
+		return -EIO;
+	}
+	if (acpi_object_out->buffer.length < out_len) {
+		dev_err(&wdev->dev, "Unexpected out buffer length.\n");
+		return -EIO;
+	}
+
+	memcpy(out, acpi_object_out->buffer.pointer, out_len);
+
+	return 0;
+}
+
+int tux_wmi_xx_8in_80out(struct wmi_device *wdev,
+			 enum tux_wmi_xx_8in_80out_methods method,
+			 union tux_wmi_xx_8in_80out_in_t *in,
+			 union tux_wmi_xx_8in_80out_out_t *out)
+{
+	return __wmi_method_buffer_out(wdev, method, in->raw, 8, out->raw, 80);
+}
+
+int tux_wmi_xx_496in_80out(struct wmi_device *wdev,
+			   enum tux_wmi_xx_496in_80out_methods method,
+			   union tux_wmi_xx_496in_80out_in_t *in,
+			   union tux_wmi_xx_496in_80out_out_t *out)
+{
+	return __wmi_method_buffer_out(wdev, method, in->raw, 496, out->raw, 80);
+}