[PATCH RFT] platform/x86: acer-wmi: add mic-mute LED via SetLedIndicator

From: Aleksandrs Bogdanovs <[email protected]>
Subject: [PATCH RFT] platform/x86: acer-wmi: add mic-mute LED via SetLedIndicator

On the Acer Aspire A517-53 (and relatives) the mic-mute key has an LED that
Windows lights to reflect the microphone state. The key itself is a plain
keyboard event (atkbd scancode 0x66), so the firmware does not drive the LED
automatically; the Windows Acer utility caught the key and toggled the LED via
a WMI method.

The LED is controlled by SetLedIndicator (WmiMethodId 12) of the
UtilityFunction class (GUID FE1DBBDA-3014-4856-870C-5B3A744BF341). The ACPI
implementation (WMBL, case 0x0C) only copies an 8-byte input buffer into BLCP
and triggers SMI port 0xD0 (CTID='BL'); all logic lives in BIOS SMM and the
input buffer format is undocumented.

This patch wires up an "acer-wmi::micmute" LED classdev (default trigger
audio-micmute) calling SetLedIndicator. Because the buffer encoding is only
known to the Windows utility, the id/state bytes are exposed as module
parameters (micmute_led, micmute_id, micmute_on, micmute_off) so the encoding
can be found without a rebuild. The LED is not registered by default.

This is sent as [RFT]: I do not run Windows and cannot capture the argument the
Acer utility passes. I am looking for a tester with the same model who can trace
the SetLedIndicator call (WMI/ETW trace or API Monitor) for mic-mute on/off.
Full analysis, decoded BMOF, disassembled SSDT, an acpidump and a sysfs probe
module are available; see the attached archive.

Signed-off-by: Aleksandrs Bogdanovs <[email protected]>
---
 drivers/platform/x86/acer-wmi.c | 85 +++++++++++++++++++++++++++++++++

--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -109,6 +109,9 @@
 #define WMID_GUID2		"95764E09-FB56-4E83-B31A-37761F60994A"
 #define WMID_GUID3		"61EF69EA-865C-4BC3-A502-A0DEBA0CB531"
 #define WMID_GUID4		"7A4DDFE7-5B5D-40B4-8595-4408E0CC7F56"
+/* UtilityFunction class: holds Get/SetLedIndicator (methods 11/12) */
+#define WMID_UTIL_GUID		"FE1DBBDA-3014-4856-870C-5B3A744BF341"
+#define WMID_UTIL_SET_LED	12
 
 /*
  * Acer ACPI event GUIDs
@@ -336,6 +339,22 @@
 static bool predator_v4;
 static u64 supported_sensors;
 
+/*
+ * Mic-mute LED (Acer Aspire A517-53 and relatives).
+ * Driven by SetLedIndicator (WmiMethodId 12) of the UtilityFunction class,
+ * GUID FE1DBBDA-3014-4856-870C-5B3A744BF341. The actual work happens in BIOS
+ * SMM (the WMBL ACPI method copies an 8-byte buffer into BLCP and triggers SMI
+ * port 0xD0, CTID='BL'), so the exact input format is undocumented. The module
+ * parameters below allow tuning the encoding at load time without a rebuild:
+ *   micmute_led    = 1   register the LED (disabled by default)
+ *   micmute_id     = indicator id (buffer byte 0)
+ *   micmute_on/off = state value (buffer byte 1)
+ */
+static bool micmute_led;
+static int micmute_id = 0x0c;
+static int micmute_on = 0x01;
+static int micmute_off = 0x00;
+
 module_param(mailled, int, 0444);
 module_param(brightness, int, 0444);
 module_param(threeg, int, 0444);
@@ -344,7 +363,15 @@
 module_param(ec_raw_mode, bool, 0444);
 module_param(cycle_gaming_thermal_profile, bool, 0644);
 module_param(predator_v4, bool, 0444);
+module_param(micmute_led, bool, 0444);
+module_param(micmute_id, int, 0444);
+module_param(micmute_on, int, 0444);
+module_param(micmute_off, int, 0444);
 MODULE_PARM_DESC(mailled, "Set initial state of Mail LED");
+MODULE_PARM_DESC(micmute_led, "Register mic-mute LED via SetLedIndicator (experimental)");
+MODULE_PARM_DESC(micmute_id, "Mic-mute LED indicator id (byte 0 of SetLedIndicator buffer)");
+MODULE_PARM_DESC(micmute_on, "Mic-mute LED 'on' value (byte 1)");
+MODULE_PARM_DESC(micmute_off, "Mic-mute LED 'off' value (byte 1)");
 MODULE_PARM_DESC(brightness, "Set initial LCD backlight brightness");
 MODULE_PARM_DESC(threeg, "Set initial state of 3G hardware");
 MODULE_PARM_DESC(force_series, "Force a different laptop series");
@@ -1946,6 +1973,57 @@
 }
 
 /*
+ * Mic-mute LED via UtilityFunction::SetLedIndicator.
+ * The method takes an 8-byte buffer; byte 0 = indicator id, byte 1 = state
+ * (values are configurable through the micmute_id/on/off module parameters
+ * because the exact format is defined by the SMM firmware and undocumented).
+ */
+static acpi_status wmid_set_led_indicator(u64 val)
+{
+	struct acpi_buffer input = { (acpi_size)sizeof(val), &val };
+
+	return wmi_evaluate_method(WMID_UTIL_GUID, 0, WMID_UTIL_SET_LED,
+				   &input, NULL);
+}
+
+static int micmute_led_set(struct led_classdev *led_cdev,
+			   enum led_brightness value)
+{
+	u64 buf = ((u64)(value ? micmute_on : micmute_off) << 8) |
+		  (micmute_id & 0xff);
+	acpi_status status;
+
+	status = wmid_set_led_indicator(buf);
+	return ACPI_SUCCESS(status) ? 0 : -EIO;
+}
+
+static struct led_classdev micmute_led_cdev = {
+	.name = "acer-wmi::micmute",
+	.max_brightness = 1,
+	.brightness_set_blocking = micmute_led_set,
+	.default_trigger = "audio-micmute",
+};
+
+static int acer_micmute_led_init(struct device *dev)
+{
+	if (!micmute_led)
+		return 0;
+	if (!wmi_has_guid(WMID_UTIL_GUID)) {
+		pr_info("micmute LED requested but UtilityFunction WMI GUID absent\n");
+		return 0;
+	}
+	return led_classdev_register(dev, &micmute_led_cdev);
+}
+
+static void acer_micmute_led_exit(void)
+{
+	if (!micmute_led || !wmi_has_guid(WMID_UTIL_GUID))
+		return;
+	micmute_led_set(&micmute_led_cdev, LED_OFF);
+	led_classdev_unregister(&micmute_led_cdev);
+}
+
+/*
  * Backlight device
  */
 static struct backlight_device *acer_backlight_device;
@@ -2775,6 +2853,10 @@
 			goto error_mailled;
 	}
 
+	err = acer_micmute_led_init(&device->dev);
+	if (err)
+		goto error_micmute;
+
 	if (has_cap(ACER_CAP_BRIGHTNESS)) {
 		err = acer_backlight_init(&device->dev);
 		if (err)
@@ -2806,6 +2888,8 @@
 	if (has_cap(ACER_CAP_BRIGHTNESS))
 		acer_backlight_exit();
 error_brightness:
+	acer_micmute_led_exit();
+error_micmute:
 	if (has_cap(ACER_CAP_MAILLED))
 		acer_led_exit();
 error_mailled:
@@ -2816,6 +2900,7 @@
 {
 	if (has_cap(ACER_CAP_MAILLED))
 		acer_led_exit();
+	acer_micmute_led_exit();
 	if (has_cap(ACER_CAP_BRIGHTNESS))
 		acer_backlight_exit();