Input: cm109 - fix handling of volume and mute buttons

The CM109 driver reported key press events of volume up / down and
record / playback mute buttons, but no release events. Report those events
properly by handling volume and mute keys seperately. For the record and
playback mute buttons, only presses are registered by the CM109, therefore
simulate press-n-release. This fixes the volume control buttons of various
USB headsets.
Signed-off-by: Florian Euchner <florian.euchner@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/cm109.c

@@ -76,8 +76,8 @@ enum {
 
 	BUZZER_ON = 1 << 5,
 
-	/* up to 256 normal keys, up to 16 special keys */
-	KEYMAP_SIZE = 256 + 16,
+	/* up to 256 normal keys, up to 15 special key combinations */
+	KEYMAP_SIZE = 256 + 15,
 };
 
 /* CM109 protocol packet */
@@ -139,7 +139,7 @@ static unsigned short special_keymap(int code)
 {
 	if (code > 0xff) {
 		switch (code - 0xff) {
-		case RECORD_MUTE:	return KEY_MUTE;
+		case RECORD_MUTE:	return KEY_MICMUTE;
 		case PLAYBACK_MUTE:	return KEY_MUTE;
 		case VOLUME_DOWN:	return KEY_VOLUMEDOWN;
 		case VOLUME_UP:		return KEY_VOLUMEUP;
@@ -312,6 +312,32 @@ static void report_key(struct cm109_dev *dev, int key)
 	input_sync(idev);
 }
 
+/*
+ * Converts data of special key presses (volume, mute) into events
+ * for the input subsystem, sends press-n-release for mute keys.
+ */
+static void cm109_report_special(struct cm109_dev *dev)
+{
+	static const u8 autorelease = RECORD_MUTE | PLAYBACK_MUTE;
+	struct input_dev *idev = dev->idev;
+	u8 data = dev->irq_data->byte[HID_IR0];
+	unsigned short keycode;
+	int i;
+
+	for (i = 0; i < 4; i++) {
+		keycode = dev->keymap[0xff + BIT(i)];
+		if (keycode == KEY_RESERVED)
+			continue;
+
+		input_report_key(idev, keycode, data & BIT(i));
+		if (data & autorelease & BIT(i)) {
+			input_sync(idev);
+			input_report_key(idev, keycode, 0);
+		}
+	}
+	input_sync(idev);
+}
+
 /******************************************************************************
  * CM109 usb communication interface
  *****************************************************************************/
@@ -357,10 +383,7 @@ static void cm109_urb_irq_callback(struct urb *urb)
 	}
 
 	/* Special keys */
-	if (dev->irq_data->byte[HID_IR0] & 0x0f) {
-		const int code = (dev->irq_data->byte[HID_IR0] & 0x0f);
-		report_key(dev, dev->keymap[0xff + code]);
-	}
+	cm109_report_special(dev);
 
 	/* Scan key column */
 	if (dev->keybit == 0xf) {