platform/x86: asus-wmi: add keyboard brightness event handler

The keyboard brightness control of Asus WMI keyboards is handled in
kernel, which leads to the shortcut going from brightness 0, to 1,
to 2, and 3.

However, for HID keyboards it is exposed as a key and handled by the
user's desktop environment. For the toggle button, this means that
brightness control becomes on/off. In addition, in the absence of a
DE, the keyboard brightness does not work.

Therefore, expose an event handler for the keyboard brightness control
which can then be used by hid-asus. Since this handler is called from
an interrupt context, defer the actual work to a workqueue.

In the process, introduce ASUS_EV_MAX_BRIGHTNESS to hold the constant
for maximum brightness since it is shared between hid-asus/asus-wmi.

Reviewed-by: Luke D. Jones <luke@ljones.dev>
Tested-by: Luke D. Jones <luke@ljones.dev>
Acked-by: Benjamin Tissoires <bentiss@kernel.org>
Reviewed-by: Denis Benato <benato.denis96@gmail.com>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
Link: https://patch.msgid.link/20260122075044.5070-11-lkml@antheas.dev
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

1 files changed, 41 insertions, 5 deletions

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index c45846be3f99..4cbd7b9806dc 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1720,6 +1720,44 @@ static void kbd_led_update_all(struct work_struct *work)
 }
 
 /*
+ * This function is called from hid-asus to inform asus-wmi of brightness
+ * changes initiated by the keyboard backlight keys.
+ */
+int asus_hid_event(enum asus_hid_event event)
+{
+	struct asus_wmi *asus;
+	int brightness;
+
+	guard(spinlock_irqsave)(&asus_ref.lock);
+	asus = asus_ref.asus;
+	if (!asus || !asus->kbd_led_registered)
+		return -EBUSY;
+
+	brightness = asus->kbd_led_wk;
+
+	switch (event) {
+	case ASUS_EV_BRTUP:
+		brightness += 1;
+		break;
+	case ASUS_EV_BRTDOWN:
+		brightness -= 1;
+		break;
+	case ASUS_EV_BRTTOGGLE:
+		if (brightness >= ASUS_EV_MAX_BRIGHTNESS)
+			brightness = 0;
+		else
+			brightness += 1;
+		break;
+	}
+
+	asus->kbd_led_wk = clamp_val(brightness, 0, ASUS_EV_MAX_BRIGHTNESS);
+	asus->kbd_led_notify = true;
+	queue_work(asus->led_workqueue, &asus->kbd_led_work);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asus_hid_event);
+
+/*
  * These functions actually update the LED's, and are called from a
  * workqueue. By doing this as separate work rather than when the LED
  * subsystem asks, we avoid messing with the Asus ACPI stuff during a
@@ -1801,13 +1839,11 @@ static void do_kbd_led_set(struct led_classdev *led_cdev, int value)
 {
 	struct asus_hid_listener *listener;
 	struct asus_wmi *asus;
-	int max_level;
 
 	asus = container_of(led_cdev, struct asus_wmi, kbd_led);
-	max_level = asus->kbd_led.max_brightness;
 
 	scoped_guard(spinlock_irqsave, &asus_ref.lock)
-		asus->kbd_led_wk = clamp_val(value, 0, max_level);
+		asus->kbd_led_wk = clamp_val(value, 0, ASUS_EV_MAX_BRIGHTNESS);
 
 	if (asus->kbd_led_avail)
 		kbd_led_update(asus);
@@ -2011,7 +2047,7 @@ static int asus_wmi_led_init(struct asus_wmi *asus)
 	asus->kbd_led.flags = LED_BRIGHT_HW_CHANGED;
 	asus->kbd_led.brightness_set_blocking = kbd_led_set;
 	asus->kbd_led.brightness_get = kbd_led_get;
-	asus->kbd_led.max_brightness = 3;
+	asus->kbd_led.max_brightness = ASUS_EV_MAX_BRIGHTNESS;
 	asus->kbd_led_avail = !kbd_led_read(asus, &led_val, NULL);
 	INIT_WORK(&asus->kbd_led_work, kbd_led_update_all);
 
@@ -4530,7 +4566,7 @@ static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
 		return;
 	}
 	if (code == NOTIFY_KBD_BRTTOGGLE) {
-		if (led_value >= asus->kbd_led.max_brightness)
+		if (led_value >= ASUS_EV_MAX_BRIGHTNESS)
 			kbd_led_set_by_kbd(asus, 0);
 		else
 			kbd_led_set_by_kbd(asus, led_value + 1);