[PATCH] platform/x86: asus-wmi: Add keyboard backlight toggle support

[Chris Chiu <chiu@endlessm.com>]

Some Asus laptops like UX550GE has hotkey (Fn+F7) for keyboard
backlight toggle. In this UX550GE, the hotkey incremet the level
of brightness for each keypress from 1 to 3, and then switch it
off when the brightness has been the max. This commit interprets
the code 0xc7 generated from hotkey to KEY_KBDILLUMUP to increment
the brightness, then pass KEY_KBDILLUMTOGGLE to user space after
the brightness max been reached for switching the led off.

https://phabricator.endlessm.com/T21390

Signed-off-by: Chris Chiu <chiu@endlessm.com>
---
 drivers/platform/x86/asus-nb-wmi.c | 1 +
 drivers/platform/x86/asus-wmi.c    | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/platform/x86/asus-nb-wmi.c b/drivers/platform/x86/asus-nb-wmi.c
index 136ff2b..14c502e 100644
--- a/drivers/platform/x86/asus-nb-wmi.c
+++ b/drivers/platform/x86/asus-nb-wmi.c
@@ -496,6 +496,7 @@ static const struct key_entry asus_nb_wmi_keymap[] = {
 	{ KE_KEY, 0xC4, { KEY_KBDILLUMUP } },
 	{ KE_KEY, 0xC5, { KEY_KBDILLUMDOWN } },
 	{ KE_IGNORE, 0xC6, },  /* Ambient Light Sensor notification */
+	{ KE_KEY, 0xC7, { KEY_KBDILLUMTOGGLE } },
 	{ KE_END, 0},
 };
 
diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 1f6e68f..b64ff90 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -67,6 +67,7 @@ MODULE_LICENSE("GPL");
 #define NOTIFY_BRNDOWN_MAX		0x2e
 #define NOTIFY_KBD_BRTUP		0xc4
 #define NOTIFY_KBD_BRTDWN		0xc5
+#define NOTIFY_KBD_BRTTOGGLE		0xc7
 
 /* WMI Methods */
 #define ASUS_WMI_METHODID_SPEC	        0x43455053 /* BIOS SPECification */
@@ -1745,6 +1746,13 @@ static void asus_wmi_notify(u32 value, void *context)
 		}
 	}
 
+	if (code == NOTIFY_KBD_BRTTOGGLE) {
+		if (asus->kbd_led_wk < asus->kbd_led.max_brightness)
+			code = NOTIFY_KBD_BRTUP;
+		else
+			code = NOTIFY_KBD_BRTTOGGLE;
+	}
+
 	if (is_display_toggle(code) &&
 	    asus->driver->quirks->no_display_toggle)
 		goto exit;
-- 
2.7.4