Broadcom Device BCM43142 Wireless Driver for Ubuntu 14.04 LTS 64Bit Desktop not working out of box

$ lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04

$ apt-cache policy network-manager
network-manager:
  Installed: 0.9.8.8-0ubuntu7
  Candidate: 0.9.8.8-0ubuntu7
  Version table:
 *** 0.9.8.8-0ubuntu7 0
        500 http://in.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

After installing Ubuntu 14.04 Desktop version 64 bit on my Dell Vostro 2520 Laptop, I expected the wirless card to automatically be detected and to be able to connect to any wireless network for seamless internet access.

However, the driver for wifi did not get automatically installed. I looked around for some information in the web and found a blog suggestion to run the following command for wifi to work:

$sudo apt-get install linux-headers-generic build-essential dkms

After running this command, I found the driver to show up in the right corner, but when I select a wifi network, I saw another error:

(1) Creating object for path '/org/freedesktop/NetworkManager/ActiveConnection/2' failed in libnm-glib.

I tried asking in the freenode ubuntu irc chatroom but did not get any solutions.

After trying out several suggestions from the chat room, nothing worked.

Workaround:
Finally, through nm-applet I clicked on "Edit Connections" and selected the wifi network I was trying to add. Then in the security settings, I typed the password for accessing the wifi and configured it.

When I unplugged my LAN and restarted wifi, it worked. Now I am able to access the wifi.

The forum member in Ubuntu chatroom suggested I file a bug:

To summarize the issue is, there is no inbuilt driver for Broadcom BCM43142 Network Controller.

Please help fix this in the next update. Let me know if you need any further information.

Thanks
Sharath

$ lsusb
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 004: ID 0c45:6473 Microdia
Bus 001 Device 003: ID 0a5c:21d7 Broadcom Corp. BCM43142 Bluetooth 4.0
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

$ lspci
00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1 (rev c4)
00:1c.3 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 4 (rev c4)
00:1c.5 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 6 (rev c4)
00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM75 Express Chipset LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller (rev 04)
07:00.0 Network controller: Broadcom Corporation BCM43142 802.11b/g/n (rev 01)
09:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 07)