[Galaxy S 4 Q&A, Help & Troubleshooting] fedex-bermu:
So, I've tried "svc wifi disable" and "svc wifi enable" with no change in behavior. Taking a deeper peek, I ran "dumpsys wifi" right after attempting to toggle wifi on, and this is what it returns:

:/ # dumpsys wifi
Wi-Fi is [invalid state]
Stay-awake conditions: 0
mMulticastEnabled 0
mMulticastDisabled 0
mInIdleMode false
mScanPending false
WifiController:
total records=18
rec[0]: time=08-05 12:05:13.663 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=<null> what=155656(0x26008)
rec[1]: time=08-05 12:05:14.168 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=<null> what=155659(0x2600b)
rec[2]: time=08-05 12:05:14.168 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=DeviceActiveState what=155656(0x26008)
rec[3]: time=08-05 12:05:16.766 processed=StaEnabledState org=DeviceActiveState dest=StaDisabledWithScanState what=155656(0x26008)
rec[4]: time=08-05 12:05:17.215 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=<null> what=155656(0x26008)
rec[5]: time=08-05 12:05:17.797 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155652(0x26004)
rec[6]: time=08-05 12:05:17.906 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155652(0x26004)
rec[7]: time=08-05 12:05:22.727 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155652(0x26004)
rec[8]: time=08-05 12:05:30.449 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155654(0x26006)
rec[9]: time=08-05 12:05:33.107 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155650(0x26002)
rec[10]: time=08-05 12:05:33.195 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155651(0x26003)
rec[11]: time=08-05 12:05:34.926 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=<null> what=155656(0x26008)
rec[12]: time=08-05 12:05:42.914 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155650(0x26002)
rec[13]: time=08-05 12:05:44.404 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155660(0x2600c)
rec[14]: time=08-05 12:05:47.703 processed=DefaultState org=StaDisabledWithScanState dest=<null> what=155654(0x26006)
rec[15]: time=08-05 12:05:57.821 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=DeviceActiveState what=155656(0x26008)
rec[16]: time=08-05 12:05:57.933 processed=StaEnabledState org=DeviceActiveState dest=StaDisabledWithScanState what=155656(0x26008)
rec[17]: time=08-05 12:05:58.042 processed=StaDisabledWithScanState org=StaDisabledWithScanState dest=<null> what=155656(0x26008)
curState=StaDisabledWithScanState
mScreenOff false
mDeviceIdle false
mPluggedType 0
mIdleMillis 900000
mSleepPolicy 2
mPersistWifiState 0
mAirplaneModeOn false
mNotificationEnabled true
mNotificationRepeatTime 0
mNotificationShown false
mNumScansSinceNetworkStateChange 0
mEnableTrafficStatsPoll false
mTrafficStatsPollToken 0
mTxPkts 0
mRxPkts 0
mDataActivity 0
Latest scan results:

Locks acquired: 0 full, 0 full high perf, 1 scan
Locks released: 0 full, 0 full high perf, 1 scan

Locks held:
Multicast Locks held:
WifiWatchdogStateMachine:
total records=0
curState=NotConnectedState
mWifiInfo: [null]
mLinkProperties: [null]
mCurrentSignalLevel: [0]
mPoorNetworkDetectionEnabled: [false]

WifiStateMachine:
total records=43
rec[0]: time=08-05 12:05:13.440 processed=DefaultState org=InitialState dest=<null> what=131154(0x20052) CMD_ENABLE_RSSI_POLL rt=53135/53135 1 0
rec[1]: time=08-05 12:05:13.440 processed=DefaultState org=InitialState dest=<null> what=69632(0x11000) AsyncChannel.CMD_CHANNEL_HALF_CONNECTED rt=53136/53136 0 0
rec[2]: time=08-05 12:05:13.770 processed=InitialState org=InitialState dest=<null> what=131083(0x2000b) CMD_START_SUPPLICANT rt=53465/53465 0 0
rec[3]: time=08-05 12:05:13.770 processed=DefaultState org=InitialState dest=<null> what=131144(0x20048) (-5)CMD_SET_OPERATIONAL_MODE rt=53465/53465 3 0
rec[4]: time=08-05 12:05:13.770 processed=DefaultState org=InitialState dest=<null> what=131085(0x2000d) (-5)CMD_START_DRIVER rt=53465/53465 0 0
rec[5]: time=08-05 12:05:15.598 processed=InitialState org=InitialState dest=<null> what=131083(0x2000b) CMD_START_SUPPLICANT rt=55294/55294 0 0
rec[6]: time=08-05 12:05:15.599 processed=DefaultState org=InitialState dest=<null> what=131144(0x20048) (-5)CMD_SET_OPERATIONAL_MODE rt=55294/55294 1 0
rec[7]: time=08-05 12:05:15.599 processed=DefaultState org=InitialState dest=<null> what=131085(0x2000d) (-5)CMD_START_DRIVER rt=55294/55294 0 0
rec[8]: time=08-05 12:05:15.599 processed=DefaultState org=InitialState dest=<null> what=131149(0x2004d) CMD_SET_HIGH_PERF_MODE rt=55294/55294 0 0
rec[9]: time=08-05 12:05:29.816 processed=InitialState org=InitialState dest=SupplicantStartingState what=131083(0x2000b) CMD_START_SUPPLICANT rt=71624/71624 0 0
rec[10]: time=08-05 12:05:29.816 processed=SupplicantStartingState org=SupplicantStartingState dest=<null> what=131144(0x20048) (-4)CMD_SET_OPERATIONAL_MODE rt=71624/71624 3 0
rec[11]: time=08-05 12:05:29.816 processed=SupplicantStartingState org=SupplicantStartingState dest=<null> what=131085(0x2000d) (-4)CMD_START_DRIVER rt=71624/71624 0 0
rec[12]: time=08-05 12:05:29.816 processed=SupplicantStartingState org=SupplicantStartingState dest=<null> what=131152(0x20050) (-4)CMD_SET_COUNTRY_CODE rt=71624/71624 1 1 ar
rec[13]: time=08-05 12:05:29.817 processed=DefaultState org=SupplicantStartingState dest=<null> what=131133(0x2003d) CMD_GET_SUPPORTED_FEATURES uid=10012 rt=71624/71624 0 0
rec[14]: time=08-05 12:05:29.817 processed=DefaultState org=SupplicantStartingState dest=<null> what=131206(0x20086) CMD_BOOT_COMPLETED rt=71625/71625 0 0
rec[15]: time=08-05 12:05:29.818 processed=SupplicantStartingState org=SupplicantStartingState dest=InitialState what=147458(0x24002) SUP_DISCONNECTION_EVENT rt=71625/71625 0 0
rec[16]: time=08-05 12:05:30.018 processed=DefaultState org=InitialState dest=<null> what=131144(0x20048) (-5)CMD_SET_OPERATIONAL_MODE rt=71826/71826 3 0
rec[17]: time=08-05 12:05:30.019 processed=DefaultState org=InitialState dest=<null> what=131085(0x2000d) (-5)CMD_START_DRIVER rt=71826/71826 0 0
rec[18]: time=08-05 12:05:30.019 processed=DefaultState org=InitialState dest=<null> what=131152(0x20050) CMD_SET_COUNTRY_CODE rt=71826/71826 1 1 ar
rec[19]: time=08-05 12:05:30.383 processed=DefaultState org=InitialState dest=<null> what=131133(0x2003d) CMD_GET_SUPPORTED_FEATURES uid=10012 rt=72191/72191 0 0
rec[20]: time=08-05 12:05:30.457 processed=DefaultState org=InitialState dest=<null> what=131143(0x20047) (-5)CMD_START_SCAN rt=72264/72264 10012 0 ic=0 proc(ms):0 cnt=0 rssi=-127 f=-1 sc=0 link=-1 tx=0.0, 0.0, 0.0 rx=0.0 fiv=0 [on:0 tx:0 rx:0 period:1530715225] from screen [on:0 period:1530715225]
rec[21]: time=08-05 12:05:33.104 processed=DefaultState org=InitialState dest=<null> what=131167(0x2005f) !CMD_SCREEN_STATE_CHANGED rt=74912/74912 1 0
rec[22]: time=08-05 12:05:33.105 processed=DefaultState org=InitialState dest=<null> what=131154(0x20052) !CMD_ENABLE_RSSI_POLL rt=74912/74912 1 0
rec[23]: time=08-05 12:05:33.105 processed=DefaultState org=InitialState dest=<null> what=131127(0x20037) !(-5)CMD_ENABLE_ALL_NETWORKS rt=74912/74912 0 0
rec[24]: time=08-05 12:05:33.105 processed=DefaultState org=InitialState dest=<null> what=131158(0x20056) !CMD_SET_SUSPEND_OPT_ENABLED rt=74912/74912 0 0
rec[25]: time=08-05 12:05:33.105 processed=DefaultState org=InitialState dest=<null> what=131129(0x20039) !(-5)CMD_CLEAR_BLACKLIST rt=74912/74912 0 0
rec[26]: time=08-05 12:05:33.193 processed=DefaultState org=InitialState dest=<null> what=131167(0x2005f) CMD_SCREEN_STATE_CHANGED rt=75000/75000 0 0
rec[27]: time=08-05 12:05:33.193 processed=DefaultState org=InitialState dest=<null> what=131154(0x20052) CMD_ENABLE_RSSI_POLL rt=75000/75000 0 0
rec[28]: time=08-05 12:05:33.193 processed=DefaultState org=InitialState dest=<null> what=131158(0x20056) CMD_SET_SUSPEND_OPT_ENABLED rt=75001/75001 1 0
rec[29]: time=08-05 12:05:34.926 processed=InitialState org=InitialState dest=<null> what=131083(0x2000b) CMD_START_SUPPLICANT rt=76734/76734 0 0
rec[30]: time=08-05 12:05:42.908 processed=DefaultState org=InitialState dest=<null> what=131167(0x2005f) !CMD_SCREEN_STATE_CHANGED rt=84716/84716 1 0
rec[31]: time=08-05 12:05:42.908 processed=DefaultState org=InitialState dest=<null> what=131154(0x20052) !CMD_ENABLE_RSSI_POLL rt=84716/84716 1 0
rec[32]: time=08-05 12:05:42.909 processed=DefaultState org=InitialState dest=<null> what=131127(0x20037) !(-5)CMD_ENABLE_ALL_NETWORKS rt=84716/84716 0 0
rec[33]: time=08-05 12:05:42.909 processed=DefaultState org=InitialState dest=<null> what=131158(0x20056) !CMD_SET_SUSPEND_OPT_ENABLED rt=84716/84716 0 0
rec[34]: time=08-05 12:05:42.909 processed=DefaultState org=InitialState dest=<null> what=131129(0x20039) !(-5)CMD_CLEAR_BLACKLIST rt=84716/84716 0 0
rec[35]: time=08-05 12:05:53.307 processed=DefaultState org=InitialState dest=<null> what=131143(0x20047) !(-5)CMD_START_SCAN rt=95114/95114 10012 1 ic=0 proc(ms):1 cnt=3 rssi=-127 f=-1 sc=0 link=-1 tx=0.0, 0.0, 0.0 rx=0.0 fiv=20000 [on:0 tx:0 rx:0 period:22850] from screen [on:0 period:1530738075]
rec[36]: time=08-05 12:05:57.928 processed=InitialState org=InitialState dest=<null> what=131083(0x2000b) !CMD_START_SUPPLICANT rt=99736/99736 0 0
rec[37]: time=08-05 12:05:57.928 processed=DefaultState org=InitialState dest=<null> what=131144(0x20048) !(-5)CMD_SET_OPERATIONAL_MODE rt=99736/99736 1 0
rec[38]: time=08-05 12:05:57.928 processed=DefaultState org=InitialState dest=<null> what=131085(0x2000d) !(-5)CMD_START_DRIVER rt=99736/99736 0 0
rec[39]: time=08-05 12:05:57.928 processed=DefaultState org=InitialState dest=<null> what=131149(0x2004d) !CMD_SET_HIGH_PERF_MODE rt=99736/99736 0 0
rec[40]: time=08-05 12:05:58.041 processed=InitialState org=InitialState dest=<null> what=131083(0x2000b) !CMD_START_SUPPLICANT rt=99849/99849 0 0
rec[41]: time=08-05 12:05:58.041 processed=DefaultState org=InitialState dest=<null> what=131144(0x20048) !(-5)CMD_SET_OPERATIONAL_MODE rt=99849/99849 3 0
rec[42]: time=08-05 12:05:58.041 processed=DefaultState org=InitialState dest=<null> what=131085(0x2000d) !(-5)CMD_START_DRIVER rt=99849/99849 0 0
curState=InitialState
SupplicantStateTracker:
total records=0
curState=UninitializedState
mAuthenticationFailuresCount 0
mAuthFailureInSupplicantBroadcast false
mNetworksDisabledDuringConnect false

mLinkProperties {LinkAddresses: [] Routes: [] DnsAddresses: [] Domains: null MTU: 0}
mWifiInfo SSID: <unknown ssid>, BSSID: <none>, MAC: 02:00:00:00:00:00, Supplicant state: UNINITIALIZED, RSSI: -127, Link speed: -1Mbps, Frequency: -1MHz, Net ID: -1, Metered hint: false, score: 0
mDhcpResults null
mNetworkInfo [type: WIFI[], state: UNKNOWN/IDLE, reason: (unspecified), extra: (none), roaming: false, failover: false, isAvailable: false]
mLastSignalLevel -1
mLastBssid null
mLastNetworkId -1
mOperationalMode 1
mUserWantsSuspendOpt true
mSuspendOptNeedsDisabled 4
Supplicant status null
mLegacyPnoEnabled false
mDriverSetCountryCode null
mConnectedModeGScanOffloadStarted false
mGScanPeriodMilli 0
mConnectionRequests 1
mUntrustedReqCount 0

Dump of WifiConfigStore
mLastPriority -1
Configured networks

WifiConfigStore - Log Begin ----
08-05 12:05:13.668 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
08-05 12:05:15.497 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
08-05 12:05:16.780 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
08-05 12:05:16.893 - p2p0: connectToSupplicant
08-05 12:05:24.888 - p2p0: connectToSupplicant
08-05 12:05:24.988 - p2p0: connectToSupplicant
08-05 12:05:25.089 - p2p0: connectToSupplicant
08-05 12:05:25.189 - p2p0: connectToSupplicant
08-05 12:05:25.290 - p2p0: connectToSupplicant
08-05 12:05:25.390 - p2p0: connectToSupplicant
08-05 12:05:25.491 - p2p0: connectToSupplicant
08-05 12:05:25.591 - p2p0: connectToSupplicant
08-05 12:05:25.692 - p2p0: connectToSupplicant
08-05 12:05:25.793 - p2p0: connectToSupplicant
08-05 12:05:25.893 - p2p0: connectToSupplicant
08-05 12:05:25.994 - p2p0: connectToSupplicant
08-05 12:05:26.094 - p2p0: connectToSupplicant
08-05 12:05:26.195 - p2p0: connectToSupplicant
08-05 12:05:26.295 - p2p0: connectToSupplicant
08-05 12:05:26.396 - p2p0: connectToSupplicant
08-05 12:05:26.496 - p2p0: connectToSupplicant
08-05 12:05:26.596 - p2p0: connectToSupplicant
08-05 12:05:26.697 - p2p0: connectToSupplicant
08-05 12:05:26.797 - p2p0: connectToSupplicant
08-05 12:05:26.898 - p2p0: connectToSupplicant
08-05 12:05:26.998 - p2p0: connectToSupplicant
08-05 12:05:27.099 - p2p0: connectToSupplicant
08-05 12:05:27.199 - p2p0: connectToSupplicant
08-05 12:05:27.300 - p2p0: connectToSupplicant
08-05 12:05:27.400 - p2p0: connectToSupplicant
08-05 12:05:27.501 - p2p0: connectToSupplicant
08-05 12:05:27.601 - p2p0: connectToSupplicant
08-05 12:05:27.702 - p2p0: connectToSupplicant
08-05 12:05:27.802 - p2p0: connectToSupplicant
08-05 12:05:27.903 - p2p0: connectToSupplicant
08-05 12:05:28.003 - p2p0: connectToSupplicant
08-05 12:05:28.104 - p2p0: connectToSupplicant
08-05 12:05:28.204 - p2p0: connectToSupplicant
08-05 12:05:28.305 - p2p0: connectToSupplicant
08-05 12:05:28.406 - p2p0: connectToSupplicant
08-05 12:05:28.506 - p2p0: connectToSupplicant
08-05 12:05:28.606 - p2p0: connectToSupplicant
08-05 12:05:28.707 - p2p0: connectToSupplicant
08-05 12:05:28.809 - p2p0: connectToSupplicant
08-05 12:05:28.909 - p2p0: connectToSupplicant
08-05 12:05:29.010 - p2p0: connectToSupplicant
08-05 12:05:29.110 - p2p0: connectToSupplicant
08-05 12:05:29.212 - p2p0: connectToSupplicant
08-05 12:05:29.314 - p2p0: connectToSupplicant
08-05 12:05:29.414 - p2p0: connectToSupplicant
08-05 12:05:29.514 - p2p0: connectToSupplicant
08-05 12:05:29.615 - p2p0: connectToSupplicant
08-05 12:05:29.715 - p2p0: connectToSupplicant
08-05 12:05:29.816 - p2p0: connectToSupplicant
08-05 12:05:33.104 - wlan0: 0:IFNAME=wlan0 SET pno 0 -> false
08-05 12:05:33.192 - wlan0: 1:IFNAME=wlan0 SET pno 0 -> false
08-05 12:05:34.824 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
08-05 12:05:42.908 - wlan0: 2:IFNAME=wlan0 SET pno 0 -> false
08-05 12:05:57.826 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
08-05 12:05:57.939 - startHal stack: - startHal - processMessage - processMsg - handleMessage - dispatchMessage - loop
WifiConfigStore - Log End ----

*** firmware logging disabled, no debug data ****
set config_wifi_enable_wifi_firmware_debugging to enable

root@i9500:/ #

In there, I see repeated attempts that the wifi service makes to start the supplicant and the driver. These are followed right away with disconnection events from the supplicant - that is to say - the supplicant never starts. And I can't be sure about the driver either. This seems to be confirmed by this line near the end, where we can see the false null mac that the service reports to the system, and the Supplicant state of "UNINITIALIZED".

mWifiInfo SSID: <unknown ssid>, BSSID: <none>, MAC: 02:00:00:00:00:00, Supplicant state: UNINITIALIZED, RSSI: -127, Link speed: -1Mbps, Frequency: -1MHz, Net ID: -1, Metered hint: false, score: 0

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