Camera key event can't wake up?

首先觀看keylayout.kl檔，每個platform名稱都不一樣，像ti omap4 為omap-keypad.kl
內容如下:

key 399 GRAVE
key 2 1
key 3 2
key 4 3
key 5 4
key 6 5
key 7 6
key 8 7
key 9 8
key 10 9
key 11 0
key 158 BACK WAKE_DROPPED
key 230 SOFT_RIGHT WAKE
key 60 SOFT_RIGHT WAKE
key 107 ENDCALL WAKE_DROPPED
key 62 ENDCALL WAKE_DROPPED
key 229 MENU WAKE_DROPPED
key 139 MENU WAKE_DROPPED
key 59 MENU WAKE_DROPPED
key 127 SEARCH WAKE_DROPPED
key 217 SEARCH WAKE_DROPPED
key 228 POUND
key 227 STAR
key 231 CALL WAKE_DROPPED
key 61 CALL WAKE_DROPPED
key 232 DPAD_CENTER WAKE_DROPPED
key 108 DPAD_DOWN WAKE_DROPPED
key 103 DPAD_UP WAKE_DROPPED
key 102 HOME WAKE
key 105 DPAD_LEFT WAKE_DROPPED
key 106 DPAD_RIGHT WAKE_DROPPED
key 115 VOLUME_UP
key 114 VOLUME_DOWN
key 116 POWER WAKE
key 212 CAMERA
....
key 16 Q
key 17 W
key 18 E
key 19 R
key 20 T
key 21 Y
key 22 U
key 23 I
key 24 O
key 25 P
key 26 LEFT_BRACKET
key 27 RIGHT_BRACKET
key 43 BACKSLASH

首先將CAMERA改成

key 212 CAMERA WAKE_DROPPED

並重開機，但神奇的是進了suspend之後按下CAMERA卻沒有wake up，但kernel卻有resume...
原來在 frameworks/policies/base/phone/com/android/internal/policy/impl/KeyguardViewMediator.java 有一段code，frameworks會阻擋特定key不亮螢幕，並在背景執行該key的動作。

     /**
     * When a key is received when the screen is off and the keyguard is showing,
     * we need to decide whether to actually turn on the screen, and if so, tell
     * the keyguard to prepare itself and poke the wake lock when it is ready.
     *
     * The 'Tq' suffix is per the documentation in {@link WindowManagerPolicy}.
     * Be sure not to take any action that takes a long time; any significant
     * action should be posted to a handler.
     *
     * @param keyCode The keycode of the key that woke the device
     * @return Whether we poked the wake lock (and turned the screen on)
     */
    public boolean onWakeKeyWhenKeyguardShowingTq(int keyCode) {
        if (DEBUG) Log.d(TAG, "onWakeKeyWhenKeyguardShowing(" + keyCode + ")");

        if (isWakeKeyWhenKeyguardShowing(keyCode)) {
            // give the keyguard view manager a chance to adjust the state of the
            // keyguard based on the key that woke the device before poking
            // the wake lock
            wakeWhenReadyLocked(keyCode);
            return true;
        } else {
            return false;
        }
    }

    private boolean isWakeKeyWhenKeyguardShowing(int keyCode) {
        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_DOWN:
            case KeyEvent.KEYCODE_MUTE:
            case KeyEvent.KEYCODE_HEADSETHOOK:
            case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
            case KeyEvent.KEYCODE_MEDIA_STOP:
            case KeyEvent.KEYCODE_MEDIA_NEXT:
            case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
            case KeyEvent.KEYCODE_MEDIA_REWIND:
            case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD:
            case KeyEvent.KEYCODE_CAMERA:
                return false;
        }
        return true;
    }

從isWakeKeyWhenKeyguardShowing ＆onWakeKeyWhenKeyguardShowingTq 可知道符合特定key將不會被wake up。