Set brightness of flash in Android

In my program I tested this:

try {               
    FileWriter mWriter = new FileWriter("/sys/class/leds/flashlight/brightness");
    mWriter.write(125);
    mWriter.flush();
} catch (Exception e) {
    Log.e(TAG, "setFlashlightEnabled failed", e);
}

I have this in the log :

01-13 14:56:30.578: E/test(603): setFlashlightEnabled failed
01-13 14:56:30.578: E/test(603): java.io.FileNotFoundException: /sys/class/leds/flashlight/brightness (Permission denied)
01-13 14:56:30.578: E/test(603):    at org.apache.harmony.luni.platform.OSFileSystem.open(Native Method)
01-13 14:56:30.578: E/test(603):    at dalvik.system.BlockGuard$WrappedFileSystem.open(BlockGuard.java:232)
01-13 14:56:30.578: E/test(603):    at java.io.FileOutputStream.<init>(FileOutputStream.java:94)
01-13 14:56:30.578: E/test(603):    at java.io.FileOutputStream.<init>(FileOutputStream.java:66)
01-13 14:56:30.578: E/test(603):    at java.io.FileWriter.<init>(FileWriter.java:80)
01-13 14:56:30.578: E/test(603):    at sad.sdsa.sdjahskdhj.TestpuissanceActivity.onClick(TestpuissanceActivity.java:87)
01-13 14:56:30.578: E/test(603):    at android.view.View.performClick(View.java)
01-13 14:56:30.578: E/test(603):    at android.view.View$PerformClick.run(View.java)
01-13 14:56:30.578: E/test(603):    at android.os.Handler.handleCallback(Handler.java)
01-13 14:56:30.578: E/test(603):    at android.os.Handler.dispatchMessage(Handler.java)
01-13 14:56:30.578: E/test(603):    at android.os.Looper.loop(Looper.java)
01-13 14:56:30.578: E/test(603):    at android.app.ActivityThread.main(ActivityThread.java)
01-13 14:56:30.578: E/test(603):    at java.lang.reflect.Method.invokeNative(Native Method)
01-13 14:56:30.578: E/test(603):    at java.lang.reflect.Method.invoke(Method.java:507)
01-13 14:56:30.578: E/test(603):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
01-13 14:56:30.578: E/test(603):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
01-13 14:56:30.578: E/test(603):    at dalvik.system.NativeStart.main(Native Method)

I have tested in ADB Shell this :

echo 125 > /sys/class/leds/flashlight/brightness

It works in root but not in normal mode.

What is the solution to change the flash output without being root?

It belongs to system and is being protected by system, so you must be a root to access.Also all Android devices dont have the same flashlight design in structure, sample like: in HTC device, it supports API for handling 3 different brightness level, but others don't...