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Nook Glowlight 4 Plus — WiFi Management Analysis

This document captures research into how com.nook.partner manages WiFi on the Nook Glowlight 4 Plus (bnrv1300, Android 8.1) and what options exist for KOReader to manage WiFi state without requiring CHANGE_WIFI_STATE permission.

Sources: decompiled APKs from the device (nookPartner.apk, nookBnEreader.apk, nookHub.apk, NookHWTest.apk, ctm.apk).

How nookPartner manages WiFi: "Direct Suspend"

The core mechanism is called Direct Suspend, gated by a Settings.System key:

power_enhance_enable  (int: 0 = off, 1 = on)

Flow when a Nook reader app opens

  1. App calls EpdPowerManager.onReaderResume() — sets a flag, schedules a 3-second timer.
  2. After 3 s → IStatusBarService.setDirectSuspend(enable=true, saveState=true, force=false).
  3. StatusBarService.saveNetworkState():
    • Saves wifiManager.isWifiEnabled() into mWifiEnabledBeforeReaderResume.
    • Saves Bluetooth enabled state into mBTEnabledBeforeReaderResume.
    • Calls wifiManager.setWifiEnabled(false) and bluetoothAdapter.disable().
    • Polls wlan.driver.status every 500 ms (up to 5 s) until WiFi is fully down.
  4. Writes power_enhance_enable = 1 to Settings.System.

Flow when the reader app pauses

After a 1-second delay → setDirectSuspend(enable=false, restoreState=true, force=false):

  • StatusBarService.restoreNetworkState() calls wifiManager.setWifiEnabled(mWifiEnabledBeforeReaderResume).
  • Clears mWifiEnabledBeforeReaderResume = null.
  • Writes power_enhance_enable = 0.

Keeping WiFi alive during a sync

IStatusBarService.setForceKeepNetworkState(true):

  • If direct suspend is currently active, immediately calls setDirectSuspend(false, true, force=true) to restore WiFi.
  • Queues the original pending direct-suspend values.
  • Sets mKeepNetworkState = true — any further setDirectSuspend calls are deferred.

setForceKeepNetworkState(false):

  • Clears the flag and re-applies the deferred direct-suspend values.

IStatusBarService AIDL

com.nook.partner exposes this as an exported bound service:

Action:  com.nook.intent.action.statusbar
Package: com.nook.partner
Class:   com.nook.partner.statusbar.StatusBarService

No android:permission attribute — any app can bind without special permissions.

Key methods relevant to WiFi:

Method Description
setDirectSuspend(bool enable, bool saveOrRestore, bool force) Enable/disable direct suspend, optionally saving/restoring WiFi+BT state
getDirectSuspend() Returns current power_enhance_enable value
setForceKeepNetworkState(bool) Temporarily prevent WiFi suppression (for network ops)
isWifiEnabledBeforeDirectSuspend() Returns the saved WiFi state
resetWifiEnabledBeforeReaderResume() Clears the saved WiFi state
settingsPutInt(String key, int value) Privileged write to Settings.System
settingsPutString(String key, String value) Privileged write to Settings.System

GlowLightService (used for warmth control) is a separate exported started service:

Action: action_set_color_temperature
Extra:  extra_color_temperature  (int 0–100)

Can KOReader use this instead of CHANGE_WIFI_STATE?

What works

  • Suppress WiFi while reading: bind to IStatusBarService, call setDirectSuspend(true, true, false) — saves current state and disables WiFi. No CHANGE_WIFI_STATE permission needed in KOReader.

  • Restore WiFi for a sync/download: call setForceKeepNetworkState(true) before the network operation, setForceKeepNetworkState(false) after. If nookPartner had suppressed WiFi, it will restore it.

  • Restore WiFi on KOReader exit: call setDirectSuspend(false, true, false) in onPause()/onStop() to restore WiFi to whatever state it was in before KOReader suppressed it.

What doesn't work

  • Turning WiFi ON from a fully-off state: if the user had WiFi off before KOReader suppressed it, setDirectSuspend(false, true) restores it to off (correct behavior), but there is no path through IStatusBarService to turn WiFi on from scratch. That requires CHANGE_WIFI_STATE.

Synchronization risks

The state is stored as a single field in StatusBarService (mWifiEnabledBeforeReaderResume) — not a stack, not reference-counted.

Scenario Risk
User manually toggles WiFi while KOReader is managing it Saved state becomes stale; on restore KOReader may override the user's intent
nookBnEreader and KOReader both use direct suspend They share one state slot; whichever calls setDirectSuspend last wins
KOReader crashes without calling setDirectSuspend(false) WiFi stays suppressed in all apps until screen is cycled off/on
User leaves KOReader without it cleaning up in onPause Same — WiFi remains off in the launcher and other apps

Practical verdict

For the intended use case — user leaves WiFi toggled ON in device settings, KOReader suppresses it while reading and restores it for syncing — the direct suspend mechanism works reliably as long as:

  1. KOReader properly calls setDirectSuspend(false, true, false) on every onPause()/onStop().
  2. The user does not manually toggle WiFi while KOReader is in the foreground.
  3. nookBnEreader is not simultaneously using the same mechanism (unlikely in practice).

The main tradeoff vs. using CHANGE_WIFI_STATE directly is that you cannot turn WiFi on from a user-initiated off state. If that use case matters, CHANGE_WIFI_STATE is still required.

Settings.System keys of interest

Key Type Description
power_enhance_enable int (0/1) Direct suspend active flag
global_2ss_set_up_ap_timeout_ms int Direct suspend timeout
screen_brightness int (0–100) Frontlight brightness
screen_brightness_color int (0–10) Warmth level (written by GlowLightService after ÷10 rescaling)
lockscreen_status int (0/1) Lock screen enabled flag