ec/lenovo/h8/ssdt: Add keyboard backlight interface

Add methods MLCG and MLCS for thinkpad_acpi kernel module.
Required for backlight or thinklight control from userspace.

Change-Id: Ia65e770e772936c9c32be33c30839a2dee2a107c
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/21002
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/ec/lenovo/h8/acpi/thinkpad.asl

@@ -19,6 +19,7 @@ Device (HKEY)
 	/* Generated by ssdt.c */
 	External (\HBDC, IntObj)
 	External (\HWAN, IntObj)
+	External (\HKBL, IntObj)
 
 	Name (_HID, EisaId ("IBM0068"))
 
@@ -228,4 +229,34 @@ Device (HKEY)
 			/* FIXME: Store state at resume */
 		}
 	}
+
+	/*
+	 * Argument is unused.
+	 * Returns the current state:
+	 *  Bit 9: Backlight HW present
+	 *  Bit 0-1: Brightness level
+	 */
+	Method (MLCG, 1)
+	{
+		If (HKBL) {
+			Store (0x200, Local0)
+			/* FIXME: Support 2bit brightness control */
+			Or (Local0, \_SB.PCI0.LPCB.EC.KBLT, Local0)
+			Return (Local0)
+		} Else {
+			Return (0)
+		}
+	}
+
+	/*
+	 * Set the current state:
+	 * Bit 0-1: Brightness level
+	 */
+	Method (MLCS, 1)
+	{
+		If (HKBL) {
+			/* FIXME: Support 2bit brightness control */
+			Store (And(Arg0, 1), \_SB.PCI0.LPCB.EC.WWEB)
+		}
+	}
 }

src/ec/lenovo/h8/ssdt.c

@@ -36,6 +36,8 @@ static char *h8_dsdt_scope(struct device *dev, const char *scope)
  */
 void h8_ssdt_generator(struct device *dev)
 {
+	struct ec_lenovo_h8_config *conf = dev->chip_info;
+
 	if (!acpi_device_path(dev))
 		return;
 
@@ -47,6 +49,8 @@ void h8_ssdt_generator(struct device *dev)
 	/* Used by thinkpad_acpi */
 	acpigen_write_name_byte("HBDC", h8_has_bdc(dev) ? ONE_OP : ZERO_OP);
 	acpigen_write_name_byte("HWAN", h8_has_wwan(dev) ? ONE_OP : ZERO_OP);
+	acpigen_write_name_byte("HKBL", (conf && conf->has_keyboard_backlight) ?
+				ONE_OP : ZERO_OP);
 
 	acpigen_pop_len(); /* Scope HKEY */
 }