[Android Software/Hacking General [Developers Only]] ShyPixie:
Tired of see so many "tweaks" that do not work, I decided to dig deeper.

Scavenging the entire Android source, I checked entries which are actually valid.

Note 1: Ignored the build.prop entries created by buildinfo.sh (default entries)

Note 2: I'll update/upgrade the topic gradually.

I accept all help, suggestions, observations, comments and so on.

Entries that DO NOT exist in the source:

(Again: I scaveged all Android source code)

ro.ril.disable.power.collapse

ro.mot.eri.losalert.delay

ro.config.hw_fast_dormancy

ro.config.hw_power_saving

windowsmgr.max_events_per_sec

persist.cust.tel.eons

ro.max.fling_velocity

ro.min.fling_velocity

ro.kernel.checkjni

dalvik.vm.verify-bytecode

debug.performance.tuning

video.accelerate.hw

ro.media.dec.jpeg.memcap

ro.config.nocheckin

profiler.force_disable_ulog

profiler.force_disable_err_rpt

ersist.sys.shutdown.mode

ro.HOME_APP_ADJ

Notes:

dalvik.vm.verify-bytecode

Previous version of the runtime supported the boolean

dalvik.vm.verify-bytecode property, but that has been

superceded by dalvik.vm.dexopt-flags.

ro.kernel.checkjni

The correct entry is ro.kernel.android.checkjni

ro.HOME_APP_ADJ

The interaction with this is been removed.

From google:

This is a process holding the home application -- we want to try

avoiding killing it, even if it would normally be in the background,

because the user interacts with it so much.

All ro.media.enc* entries

A more elegant alternative would be to edit /system/etc/media_profiles.xml

Valid entries on CyanogenMod and AOSP:

dalvik.vm.checkjni and ro.kernel.android.checkjni

platform_frameworks_base/core/jni/AndroidRuntime.cpp (480:489/466:475)

property_get("dalvik.vm.checkjni", propBuf, "");
if (strcmp(propBuf, "true") == 0) {
checkJni = true;
} else if (strcmp(propBuf, "false") != 0) {
/* property is neither true nor false; fall back on kernel parameter */
property_get("ro.kernel.android.checkjni", propBuf, "");
if (propBuf[0] == '1') {
checkJni = true;
}
}

wifi.supplicant_scan_interval

android_external_wpa_supplicant/wpa_supplicant.c (2459:2460)

if (property_get("wifi.supplicant_scan_interval", scan_prop, "5") != 0) {
wpa_s->scan_interval = (int)strtol(scan_prop, &endp, 0);

service.adb.tcp.port

platform_system_core/adb/adb.c (1366:1372/1350:1356)

// If one of these properties is set, also listen on that port
// If one of the properties isn't set and we couldn't listen on usb,
// listen on the default port.
property_get("service.adb.tcp.port", value, "");
if (!value[0]) {
property_get("persist.adb.tcp.port", value, "");
}

ro.sf.lcd_density and qemu.sf.lcd_density

platform_frameworks_base/core/java/android/util/DisplayMetrics.java (286:294)

private static int getDeviceDensity() {
// qemu.sf.lcd_density can be used to override ro.sf.lcd_density
// when running in the emulator, allowing for dynamic configurations.
// The reason for this is that ro.sf.lcd_density is write-once and is
// set by the init process when it parses build.prop before anything else.
return SystemProperties.getInt("qemu.sf.lcd_density",
SystemProperties.getInt("ro.sf.lcd_density", DENSITY_DEFAULT));
}
}

debug.sf.nobootanimation

platform_frameworks_base/cmds/bootanimation/bootanimation_main.cpp (45:49)

char value[PROPERTY_VALUE_MAX];
property_get("debug.sf.nobootanimation", value, "0");
int noBootAnimation = atoi(value);
ALOGI_IF(noBootAnimation, "boot animation disabled");

persist.adb.notify

Cyanogen: android_frameworks_base/services/java/com/android/server/usb/UsbDeviceManager.java (747:753)

if (mAdbEnabled && mConnected) {
if ("0".equals(SystemProperties.get("persist.adb.notify"))
|| Settings.Secure.getInt(mContext.getContentResolver(),
Settings.Secure.ADB_NOTIFY, 1) == 0)
return;

AOSP: android_frameworks_base/services/java/com/android/server/usb/UsbDeviceManager.java (714:715)

if (mAdbEnabled && mConnected) {
if ("0".equals(SystemProperties.get("persist.adb.notify"))) return;

net.rmnet0.dns* and net.dns*

This is ok for Wifi and 2G/3G conection

wifi.supplicant_scan_interval

android_external_wpa_supplicant/wpa_supplicant.c (2459:2460)

if (property_get("wifi.supplicant_scan_interval", scan_prop, "5") != 0) {
wpa_s->scan_interval = (int)strtol(scan_prop, &endp, 0);

Valid entries only on CyanogenMod:

persist.sys.purgeable_assets

android_frameworks_base/core/jni/android/graphics/BitmapFactory.cpp (632:634)

char value[PROPERTY_VALUE_MAX];
property_get("persist.sys.purgeable_assets", value, "0");
mPurgeableAssets = atoi(value) == 1;

persist.sys.use_dithering

android_packages_app_CMParts/src/com/cyanogenmod/cmparts/activities/PerformancesettingsActivity.java (102)

String useDithering = SystemProperties.get(USE_DITHERING_PERSIST_PROP, USE_DITHERING_DEFAULT);

persist.sys.jit-mode (Only "fast" and "portable" modes)

android_packages_app_CMParts/src/com/cyanogenmod/cmparts/activities/PerformancesettingsActivity.java (96:99)

mJitPref = (CheckBoxPreference) prefSet.findPreference(JIT_PREF);
String jitMode = SystemProperties.get(JIT_PERSIST_PROP,
SystemProperties.get(JIT_PROP, JIT_ENABLED));
mJitPref.setChecked(JIT_ENABLED.equals(jitMode));

pm.sleep_mode (Do not work on Non-MSM chipsets)

See sleep modes on device kernel in pm-data.c and pm.h

:highfive:

Some background info:

XLOUD, ClearAudio

If, and ONLY if your phone support xloud on stock ROM, is highly probable that this is ported for CyanogenMod and AOSP based roms, because these custom roms use proprietary drivers, firmwares, frameworks, app....

To enable, use this:

ro.semc.sound_effects_enabled=true
ro.semc.xloud.supported=true
persist.service.xloud.enable=1

The same is valid for ClearAudio. To enable use this:

ro.semc.sound_effects_enabled=true
ro.semc.clearaudio.supported=true
persist.service.clearaudio.enable=1