linux-kernel - [PATCH] asus-wmi: fixup screenpad brightness

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Message-ID: <20250525204214.104030-1-luke@ljones.dev>
Date: Sun, 25 May 2025 22:42:14 +0200
From: Luke Jones <luke@...nes.dev>
To: linux-kernel@...r.kernel.org
Cc: hdegoede@...hat.com,
	ilpo.jarvinen@...ux.intel.com,
	platform-driver-x86@...r.kernel.org,
	Luke Jones <luke@...nes.dev>
Subject: [PATCH] asus-wmi: fixup screenpad brightness

Fix up some inconsistent behaviour involving the screenpad on some
ASUS laptops. This fixes:
- illogical screen off control (0/1 flipped depending on WMI state)
- bad brightness depending on the last screenpad power state
- incorrect brightness scaling

Signed-off-by: Luke Jones <luke@...nes.dev>
---
 drivers/platform/x86/asus-wmi.c | 52 +++++++++++++--------------------
 1 file changed, 21 insertions(+), 31 deletions(-)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index f52884e90759..cec509171971 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -123,7 +123,6 @@ module_param(fnlock_default, bool, 0444);
 #define NVIDIA_TEMP_MIN		75
 #define NVIDIA_TEMP_MAX		87
 
-#define ASUS_SCREENPAD_BRIGHT_MIN 20
 #define ASUS_SCREENPAD_BRIGHT_MAX 255
 #define ASUS_SCREENPAD_BRIGHT_DEFAULT 60
 
@@ -4239,43 +4238,37 @@ static int read_screenpad_brightness(struct backlight_device *bd)
 		return err;
 	/* The device brightness can only be read if powered, so return stored */
 	if (err == BACKLIGHT_POWER_OFF)
-		return asus->driver->screenpad_brightness - ASUS_SCREENPAD_BRIGHT_MIN;
+		return bd->props.brightness;
 
 	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &retval);
 	if (err < 0)
 		return err;
 
-	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK) - ASUS_SCREENPAD_BRIGHT_MIN;
+	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK);
 }
 
 static int update_screenpad_bl_status(struct backlight_device *bd)
 {
-	struct asus_wmi *asus = bl_get_data(bd);
-	int power, err = 0;
+	int err = 0;
 	u32 ctrl_param;
 
-	power = read_screenpad_backlight_power(asus);
-	if (power < 0)
-		return power;
-
-	if (bd->props.power != power) {
-		if (power != BACKLIGHT_POWER_ON) {
-			/* Only brightness > 0 can power it back on */
-			ctrl_param = asus->driver->screenpad_brightness - ASUS_SCREENPAD_BRIGHT_MIN;
-			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT,
-						    ctrl_param, NULL);
-		} else {
-			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
-		}
-	} else if (power == BACKLIGHT_POWER_ON) {
-		/* Only set brightness if powered on or we get invalid/unsync state */
-		ctrl_param = bd->props.brightness + ASUS_SCREENPAD_BRIGHT_MIN;
+	ctrl_param = bd->props.brightness;
+	if (ctrl_param >= 0 && bd->props.power) {
+		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 1,
+					    NULL);
+		if (err < 0)
+			return err;
+		ctrl_param = bd->props.brightness;
 		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT, ctrl_param, NULL);
+		if (err < 0)
+			return err;
 	}
 
-	/* Ensure brightness is stored to turn back on with */
-	if (err == 0)
-		asus->driver->screenpad_brightness = bd->props.brightness + ASUS_SCREENPAD_BRIGHT_MIN;
+	if (!bd->props.power) {
+		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
+		if (err < 0)
+			return err;
+	}
 
 	return err;
 }
@@ -4293,22 +4286,19 @@ static int asus_screenpad_init(struct asus_wmi *asus)
 	int err, power;
 	int brightness = 0;
 
-	power = read_screenpad_backlight_power(asus);
+	power = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_SCREENPAD_POWER);
 	if (power < 0)
 		return power;
 
-	if (power != BACKLIGHT_POWER_OFF) {
+	if (power) {
 		err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &brightness);
 		if (err < 0)
 			return err;
 	}
-	/* default to an acceptable min brightness on boot if too low */
-	if (brightness < ASUS_SCREENPAD_BRIGHT_MIN)
-		brightness = ASUS_SCREENPAD_BRIGHT_DEFAULT;
 
 	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW; /* ensure this bd is last to be picked */
-	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX - ASUS_SCREENPAD_BRIGHT_MIN;
+	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX;
 	bd = backlight_device_register("asus_screenpad",
 				       &asus->platform_device->dev, asus,
 				       &asus_screenpad_bl_ops, &props);
@@ -4319,7 +4309,7 @@ static int asus_screenpad_init(struct asus_wmi *asus)
 
 	asus->screenpad_backlight_device = bd;
 	asus->driver->screenpad_brightness = brightness;
-	bd->props.brightness = brightness - ASUS_SCREENPAD_BRIGHT_MIN;
+	bd->props.brightness = brightness;
 	bd->props.power = power;
 	backlight_update_status(bd);
 
-- 
2.49.0