platform/x86: ideapad-laptop: Add support for keyboard backlights using KBLC ACPI symbol

Newer Lenovo laptops seem to use the KBLC symbol to control the backlight
Add support for handling the keyboard backlight on these devices

Signed-off-by: Stuart Hayhurst <stuart.a.hayhurst@gmail.com>
Link: https://lore.kernel.org/r/20230827161940.485200-1-stuart.a.hayhurst@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Author: stuarthayhurst

drivers/platform/x86/ideapad-laptop.c

@@ -10,6 +10,7 @@
 
 #include <linux/acpi.h>
 #include <linux/backlight.h>
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/bug.h>
 #include <linux/debugfs.h>
@@ -85,6 +86,31 @@ enum {
 	SALS_FNLOCK_OFF       = 0xf,
 };
 
+/*
+ * These correspond to the number of supported states - 1
+ * Future keyboard types may need a new system, if there's a collision
+ * KBD_BL_TRISTATE_AUTO has no way to report or set the auto state
+ * so it effectively has 3 states, but needs to handle 4
+ */
+enum {
+	KBD_BL_STANDARD      = 1,
+	KBD_BL_TRISTATE      = 2,
+	KBD_BL_TRISTATE_AUTO = 3,
+};
+
+#define KBD_BL_QUERY_TYPE		0x1
+#define KBD_BL_TRISTATE_TYPE		0x5
+#define KBD_BL_TRISTATE_AUTO_TYPE	0x7
+
+#define KBD_BL_COMMAND_GET		0x2
+#define KBD_BL_COMMAND_SET		0x3
+#define KBD_BL_COMMAND_TYPE		GENMASK(7, 4)
+
+#define KBD_BL_GET_BRIGHTNESS		GENMASK(15, 1)
+#define KBD_BL_SET_BRIGHTNESS		GENMASK(19, 16)
+
+#define KBD_BL_KBLC_CHANGED_EVENT	12
+
 struct ideapad_dytc_priv {
 	enum platform_profile_option current_profile;
 	struct platform_profile_handler pprof;
@@ -122,6 +148,7 @@ struct ideapad_private {
 	} features;
 	struct {
 		bool initialized;
+		int type;
 		struct led_classdev led;
 		unsigned int last_brightness;
 	} kbd_bl;
@@ -242,6 +269,16 @@ static int exec_sals(acpi_handle handle, unsigned long arg)
 	return exec_simple_method(handle, "SALS", arg);
 }
 
+static int exec_kblc(acpi_handle handle, unsigned long arg)
+{
+	return exec_simple_method(handle, "KBLC", arg);
+}
+
+static int eval_kblc(acpi_handle handle, unsigned long cmd, unsigned long *res)
+{
+	return eval_int_with_arg(handle, "KBLC", cmd, res);
+}
+
 static int eval_dytc(acpi_handle handle, unsigned long cmd, unsigned long *res)
 {
 	return eval_int_with_arg(handle, "DYTC", cmd, res);
@@ -1275,16 +1312,47 @@ static void ideapad_backlight_notify_brightness(struct ideapad_private *priv)
 /*
  * keyboard backlight
  */
+static int ideapad_kbd_bl_check_tristate(int type)
+{
+	return (type == KBD_BL_TRISTATE) || (type == KBD_BL_TRISTATE_AUTO);
+}
+
 static int ideapad_kbd_bl_brightness_get(struct ideapad_private *priv)
 {
-	unsigned long hals;
+	unsigned long value;
 	int err;
 
-	err = eval_hals(priv->adev->handle, &hals);
+	if (ideapad_kbd_bl_check_tristate(priv->kbd_bl.type)) {
+		err = eval_kblc(priv->adev->handle,
+				FIELD_PREP(KBD_BL_COMMAND_TYPE, priv->kbd_bl.type) |
+				KBD_BL_COMMAND_GET,
+				&value);
+
+		if (err)
+			return err;
+
+		/* Convert returned value to brightness level */
+		value = FIELD_GET(KBD_BL_GET_BRIGHTNESS, value);
+
+		/* Off, low or high */
+		if (value <= priv->kbd_bl.led.max_brightness)
+			return value;
+
+		/* Auto, report as off */
+		if (value == priv->kbd_bl.led.max_brightness + 1)
+			return 0;
+
+		/* Unknown value */
+		dev_warn(&priv->platform_device->dev,
+			 "Unknown keyboard backlight value: %lu", value);
+		return -EINVAL;
+	}
+
+	err = eval_hals(priv->adev->handle, &value);
 	if (err)
 		return err;
 
-	return !!test_bit(HALS_KBD_BL_STATE_BIT, &hals);
+	return !!test_bit(HALS_KBD_BL_STATE_BIT, &value);
 }
 
 static enum led_brightness ideapad_kbd_bl_led_cdev_brightness_get(struct led_classdev *led_cdev)
@@ -1296,7 +1364,21 @@ static enum led_brightness ideapad_kbd_bl_led_cdev_brightness_get(struct led_cla
 
 static int ideapad_kbd_bl_brightness_set(struct ideapad_private *priv, unsigned int brightness)
 {
-	int err = exec_sals(priv->adev->handle, brightness ? SALS_KBD_BL_ON : SALS_KBD_BL_OFF);
+	int err;
+	unsigned long value;
+	int type = priv->kbd_bl.type;
+
+	if (ideapad_kbd_bl_check_tristate(type)) {
+		if (brightness > priv->kbd_bl.led.max_brightness)
+			return -EINVAL;
+
+		value = FIELD_PREP(KBD_BL_SET_BRIGHTNESS, brightness) |
+			FIELD_PREP(KBD_BL_COMMAND_TYPE, type) |
+			KBD_BL_COMMAND_SET;
+		err = exec_kblc(priv->adev->handle, value);
+	} else {
+		err = exec_sals(priv->adev->handle, brightness ? SALS_KBD_BL_ON : SALS_KBD_BL_OFF);
+	}
 
 	if (err)
 		return err;
@@ -1349,8 +1431,13 @@ static int ideapad_kbd_bl_init(struct ideapad_private *priv)
 
 	priv->kbd_bl.last_brightness = brightness;
 
+	if (ideapad_kbd_bl_check_tristate(priv->kbd_bl.type)) {
+		priv->kbd_bl.led.max_brightness = 2;
+	} else {
+		priv->kbd_bl.led.max_brightness = 1;
+	}
+
 	priv->kbd_bl.led.name                    = "platform::" LED_FUNCTION_KBD_BACKLIGHT;
-	priv->kbd_bl.led.max_brightness          = 1;
 	priv->kbd_bl.led.brightness_get          = ideapad_kbd_bl_led_cdev_brightness_get;
 	priv->kbd_bl.led.brightness_set_blocking = ideapad_kbd_bl_led_cdev_brightness_set;
 	priv->kbd_bl.led.flags                   = LED_BRIGHT_HW_CHANGED;
@@ -1461,6 +1548,7 @@ static void ideapad_acpi_notify(acpi_handle handle, u32 event, void *data)
 		case 2:
 			ideapad_backlight_notify_power(priv);
 			break;
+		case KBD_BL_KBLC_CHANGED_EVENT:
 		case 1:
 			/*
 			 * Some IdeaPads report event 1 every ~20
@@ -1562,13 +1650,31 @@ static void ideapad_check_features(struct ideapad_private *priv)
 			if (test_bit(HALS_FNLOCK_SUPPORT_BIT, &val))
 				priv->features.fn_lock = true;
 
-			if (test_bit(HALS_KBD_BL_SUPPORT_BIT, &val))
+			if (test_bit(HALS_KBD_BL_SUPPORT_BIT, &val)) {
 				priv->features.kbd_bl = true;
+				priv->kbd_bl.type = KBD_BL_STANDARD;
+			}
 
 			if (test_bit(HALS_USB_CHARGING_SUPPORT_BIT, &val))
 				priv->features.usb_charging = true;
 		}
 	}
+
+	if (acpi_has_method(handle, "KBLC")) {
+		if (!eval_kblc(priv->adev->handle, KBD_BL_QUERY_TYPE, &val)) {
+			if (val == KBD_BL_TRISTATE_TYPE) {
+				priv->features.kbd_bl = true;
+				priv->kbd_bl.type = KBD_BL_TRISTATE;
+			} else if (val == KBD_BL_TRISTATE_AUTO_TYPE) {
+				priv->features.kbd_bl = true;
+				priv->kbd_bl.type = KBD_BL_TRISTATE_AUTO;
+			} else {
+				dev_warn(&priv->platform_device->dev,
+					 "Unknown keyboard type: %lu",
+					 val);
+			}
+		}
+	}
 }
 
 #if IS_ENABLED(CONFIG_ACPI_WMI)